LOS ANGELES >> A Houston-based oil company and two subsidiaries were indicted Wednesday for a crude spill that fouled Southern California waters and beaches in October, an event federal prosecutors say was caused by a series of negligent acts that led to an hours-long leak despite alarms that should have alerted workers to a pipeline rupture.

Amplify Energy Corp. and its two companies that operate three oil rigs and a pipeline off Long Beach each were charged by a federal grand jury with a single misdemeanor count of illegally discharging oil.

Investigators believe the pipeline was weakened when a cargo ship’s anchor snagged it in high winds in January, months before it ultimately ruptured Oct. 1, spilling up to about 25,000 gallons (94,600 liters) of crude oil in the ocean.

The indictment said the companies were negligent six ways, including failing to respond to eight leak detection system alarms over a 13-hour period that should have alerted them to the spill and would have minimized the damage. Instead, the pipeline was shut down after each alarm and then restarted, spewing more oil into the ocean.

Amplify said in a statement that workers onshore and offshore responded to what they believed were false alarms. The system wasn’t functioning properly because it was signaling a potential leak at the platform where no leak was occurring, the company said.

The leak, in fact, was from a section of undersea pipe 4 miles (6.44 kilometers) miles away, Amplify said.

“Had the crew known there was an actual oil spill in the water, they would have shut down the pipeline immediately,” the company said.

The Associated Press first reported last week that Amplify’s leak detection system was not fully functional. At the time, the company declined to explain what that meant.

The first alarm sounded at 4:10 p.m. Oct. 1, but the leak was not discovered until well after sunrise the next morning and reported about 9 a.m. Citizens on shore called 911 to report the strong smell of crude that first afternoon, and an anchored cargo vessel reported a large sheen on the water before sunset.

Local authorities who went looking for a spill Oct. 1 didn’t find it. The Coast Guard said it was too dark to go out and search for the spill by the time they received a report about it. They went out after sunrise, finding it around the time the company reported it.

Even after the eighth and final alarm sounded, the pipeline operated for nearly an hour in the early morning, prosecutors said. Prosecutors said the pipeline was understaffed and crew had not been sufficiently trained in the leak detection system and were fatigued.

It’s not clear why it took so long for the 1/2-inch (1.25-centimeter) thick steel line to leak after the apparent anchor incident, or whether another anchor strike or other incident led to the rupture and spill.

But experts said a properly functioning leak detection system might have been able to catch things that were amiss before an oil sheen spotted on the surface led to the leak’s discovery.

The indictment’s description of company personnel as fatigued pointed to a long-standing industry problem that pipeline expert Ramanan Krishnamoorti with the University of Houston said was “inexcusable.”

“Fatigue and overworked staff is old and trite and inexcusable,” he said. “This has been demonstrated over and over again as being the single most important vulnerability.”

The spill came ashore at Huntington Beach and forced about a weeklong closure of the city’s beaches and others along the Orange County coast. Fishing in the affected area resumed only recently, after testing confirmed fish did not have unsafe levels of oil toxins.

If convicted, the charge carries up to five years of probation for the corporation and fines that could total millions of dollars.