INCHEON, South Korea >> The doomed ferry Sewol exceeded its cargo limit on 246 trips — nearly every voyage it made in which it reported cargo — in the 13 months before it sank, according to documents that reveal the regulatory failures that allowed passengers by the hundreds to set off on an unsafe vessel. And it may have been more overloaded than ever on its final journey.

One private, industry-connected entity recorded the weights. Another set the weight limit. Neither appears to have had any idea what the other was doing. And they are but two parts of a maritime system that failed passengers April 16 when the ferry sank, leaving more than 300 people missing or dead.

The disaster has exposed enormous safety gaps in South Korea’s monitoring of domestic passenger ships, which is in some ways less rigorous than its rules for ships that handle only cargo. Collectively, the country’s regulators held more than enough information to conclude that the Sewol was routinely overloaded, but because they did not share that data and were not required to do so, it was practically useless.

The Korean Register of Shipping examined the Sewol early last year as it was being redesigned to handle more passengers. The register slashed the ship’s cargo capacity by more than half, to 987 tons, and said the vessel needed to carry more than 2,000 tons of water to stay balanced.

But the register gave its report only to the ship owner, Chonghaejin Marine Co. Ltd. Neither the coast guard nor the Korean Shipping Association, which regulates and oversees departures and arrivals of domestic passenger ships, appear to have had any knowledge of the new limit before the disaster.

“That’s a blind spot in the law,” said Lee Kyu-Yeul, professor emeritus at Seoul National University’s Department of Naval Architecture and Ocean Engineering.

Chonghaejin reported much greater cargo capacity to the shipping association: 3,963 tons, according to a coast guard official in Incheon who had access to the documentation but declined to release it.

Since the redesigned ferry began operating in March 2013, it made nearly 200 round trips — 394 individual voyages — from Incheon port near Seoul to the southern island of Jeju. On 246 of those voyages, the Sewol exceeded the 987-ton limit, according to documents from Incheon port.

The limit may have been exceeded even more frequently than that. In all but one of the other 148 trips, zero cargo was recorded. It is not mandatory for passenger ferries to report cargo to the port operator, which gathers the information to compile statistics and not for safety purposes.

More than 2,000 tons of cargo was reported on 136 of the Sewol’s trips, and it topped 3,000 tons 12 times. But the records indicate it never carried as much as it did on its final disastrous voyage: Moon Ki-han, a vice president at Union Transport Co, the company that loaded the ship, has said it was carrying an estimated 3,608 tons of cargo.

The port operator has no record of the cargo from the Sewol’s last voyage. Ferry operators submit that information only after trips are completed. In that respect, the rules for domestic passenger ships are looser than those for cargo-only vessels, which must report cargo before they depart.

Details from the port documents were first reported by the South Korean newspaper Kukmin Daily.

In paperwork filed before the Sewol’s last voyage, Capt. Lee Joon-seok reported a much smaller final load than the one Moon described, according to a Coast Guard official who had access to the report but refused to provide a copy to the Associated Press. The paperwork said the Sewol was loaded with 150 cars and 657 tons of cargo.

That would fall within the 987-ton limit, but it’s clearly inaccurate: The coast guard has found 180 cars in the water.

An official with the Korea Shipping Association’s safety team said it is beyond the association’s capacity to determine whether a ship is carrying too much cargo. He spoke on condition of anonymity because he wasn’t allowed to discuss the Sewol case as it is being investigated.

“What we can do is to see the load line is not submerged,” he said. The load line, a marking on the outside of a vessel, indicates whether a ship is overloaded, but it does not show whether it has the sort of balance between cargo and ballast that the register report said was necessary.

“The only person on any vessel who knows the exact cargo safety limit, excluding ballast water, fuel, passengers and others, is the first mate,” the official said.

All 15 surviving crew members involved in the ferry’s navigation have been arrested, accused of negligence and failing to protect passengers. Prosecutors also detained three employees of the ferry owner who handled cargo, and have raided the offices of the ship owner, the shipping association and the register. Heads of the shipping association and the register offered to resign in the wake of the disaster.

The cause of the sinking remains under investigation, but experts have said that if the ship were severely overloaded, even a small turn could cause it to lose its balance. Tracking data show the ship made a 45-degree turn around the time it began sinking; crew members have reportedly said that something went wrong with the steering as they attempted a much less severe turn.

Some experts say the Sewol never should have been cleared to operate after last year’s redesign because the owner would not be able to make money under the register’s new cargo limits.

The ferry operator “was trying to make a profit by overloading cargos,” said Kim Gil-soo, a professor at Korea Maritime and Ocean University in Busan, “and public agencies that should have monitored did not monitor that.”

According to South Korean law, the association may report violations to either the coast guard or the state-run port operator, but both entities said they were never told of excessive cargo on the Sewol. The shipping association has refused to say how often it has reported violations.

A coast guard official said the shipping association should have reported any excessive cargo to the operator of Incheon port, where the Sewol last departed. An official with the port operator says it is the coast guard that should have been alerted. The coast guard official spoke on condition of anonymity, saying he was not authorized to speak about matters under investigation; the port official refused to provide his name.

South Korea, unlike many other countries, relies on a private industry-affiliated body to determine whether a ship is safe to sail. The shipping association, whose members are shipping companies and ship operators, took on that responsibility in 1973, following a 1970 sinking in which about 320 people died.

Captains submit paperwork to the association indicating how much cargo is on board as well as crew and passengers.

The shipping association, which also oversees crew education, is partly government-funded, but its biggest business is selling insurance to its members.

Its website says about 75 percent of its 110 billion won ($107 million) budget for 2014 was allocated to its insurance department. The budget for the department dealing with domestic passenger ship safety was 7.4 billion won ($7.2 million). The association has 71 safety inspectors at 13 South Korean ports and its headquarters.

Many of the association’s high-level officials come from the Ministry of Ocean and Fisheries, which some say makes it tough for the ministry to scrutinize the group. Ministry officials may be reluctant to question association officials who are former senior public servants, or even their former bosses.

The register, which made the cargo limit evaluation, also is a private entity.

In Europe, North America and Japan, regulation is generally done by public bodies such as the U.S. Coast Guard and the U.K.’s Maritime and Coastal Agency. In Japan, the government checks ships once a year, and conducts unannounced inspections of crew qualification and emergency training.

At the same time, it’s common for governments to rely on ship captains to report their loads accurately. It would be virtually impossible to check every boat, experts say.

Since the Sewol disaster, the oceans ministry has been considering taking the job of overseeing passenger-ship safety away from the shipping association, ministry official Kwon Jun-young said. Kwon said they are discussing which agency or agencies should take up on the job.

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Associated Press writers Jung-yoon Choi in Seoul, Sylvia Hui in London and Yuri Kageyama in Tokyo contributed to this report.