A new federal report details what Hawaii-based Coast Guard officials have already said plainly for months: The massive boats harvesting tuna in foreign Pacific waters are among the most dangerous U.S.-flagged commercial fishing boats for their workers, the vast majority of whom are foreign nationals.

The report, commissioned by the Coast Guard, examines the 40 industrial tuna vessels that make up what’s called the "distant-water tuna fleet," which operates in those far-flung waters under international treaty. The fleet is different from the longliners based in Honolulu, which the Coast Guard has described as a safer operation.

The National Institute for Occupational Safety and Health found that 14 crew members and two others who technically weren’t crew died in accidents — and 20 others suffered traumatic injuries — between 2006 and 2012 aboard the distant-water boats, giving the fleet one of the highest mortality rates in the nation for commercial fleets. The largest leading cause of the death among the tuna boats, also known as purse seiners, came from crew members falling overboard, the report further found.

Many of the deaths could have been avoided if crew members had worn personal floating devices, it added.

Despite being U.S.-flagged boats, many of the distant-water fleet purse seiner vessels, which average 28 crew members, typically have only one American aboard: the captain.

The practice is entirely legal, but it helps create the language barriers cited in the Coast Guard’s own reports as being a problem during emergencies at sea. Officials with South Pacific Tuna Corp., a U.S.- and Taiwanese-owned company that operates 14 of the 40 industrial purse seiners in the fleet, say they need special legal exemptions that allow all but one crew member to be foreign nationals to stay competitive in the global tuna industry.

The NIOSH report elaborates on deaths in the fleet that were mentioned in previous reports prepared by the Coast Guard for Congress. For instance, it turns out a crew member who succumbed to "confined-space gasses," as outlined in the Coast Guard reports, died from hydrogen sulfide poisoning while cleaning a holding tank with decaying fish mass, the NIOSH report explains.

An 80-pound tuna that fell from vessel nets, striking a worker in the head and killing him, was frozen — and it broke the crew member’s hard hat, the new report states.

The NIOSH report also comes after the Coast Guard in March fined South Pacific Tuna Corp., stemming from 2012 inspections that found the company had repeatedly used unlicensed foreign nationals to illegally serve as engineers and chief mates on five of its boats.

Vessels managed by the company "continue to support ongoing efforts to bring improvements and along with other leading US Fleets in other fisheries participate on the Coast Guard National Safety council," company principal J. Douglas Hines said in a statement Friday. "We appreciate recommendations to improve vessel safety performance and over past years have worked closely with US agencies as well as others to ensure safety protocols exceed regulatory requirements."

Hines also said the company’s vessels operate nearly year-round, while many of the fleets it was compared to are highly seasonal.

Nonetheless, the deep-­water boats have raised considerable concern among local Coast Guard officials.

"This fleet has a safety problem," Coast Guard Capt. Chris Woodley said in March. "This is not your mom-and-pop fishing operation. It’s a very complex, dangerous operation, and so one of the key things is manning. You need to have safe boats and good people to operate your boats."