Nine days after the scuba boat Conception went down in flames with 34 people trapped below deck in one of the deadliest disasters in California maritime history, a federal grand jury began looking into whether a crime had been committed.

Now, a year after the Sept. 2 tragedy, investigations into the cause of the pre-dawn blaze and whether someone is to blame are still ongoing, though court documents say criminal charges are imminent.

The captain of the boat, who could face an unusual federal manslaughter charge, was briefed in July on the evidence prosecutors have against him. It’s the type of meeting often used to persuade a suspect to plead guilty, lawyers for the boat’s owners said last week in a related lawsuit.

An attorney for Capt. Jerry Boylan and federal prosecutors declined to comment on the disclosure.

The Conception was carrying 33 passengers on a Labor Day weekend scuba diving expedition near an island off Santa Barbara. The fire broke out while passengers were sleeping and quickly swept through the vessel.

Boylan and four crew members barely escaped after trying in vain to save the others, authorities said. Boylan made a mayday call at 3:14 a.m. saying, “I can’t breathe,” before abandoning ship.

All the passengers and one crew member perished in the bunk room beneath deck. It’s unclear if any had time to try to escape. Coroners said they died from smoke inhalation before their bodies were burned.

All six crew members were asleep when the fire broke out, according to the National Transportation Safety Board. If that’s the case, it would violate Coast Guard regulations requiring a roving watch.

“The lack of a night watch was an outrageous oversight,” said Jeffrey Goodman, a lawyer representing family members of nine victims.

Legal experts said prosecutors are likely trying to apply an obscure federal law known as the Seaman’s Manslaughter Statute that predates the Civil War and was enacted to punish negligent captains, engineers and pilots for deadly steamboat accidents that killed thousands.

Prosecutors would only need to prove simple negligence or misconduct on the part of the captain or crew. Conviction carries a penalty of up to 10 years in prison.

The lawsuit filings also revealed that the company that operated the boat and the couple who own it, Glen and Dana Fritzler, have offered to settle the lawsuit with dozens of victims’ family members.

Goodman said settlement discussions were preliminary and attorneys for victims were still trying to find the cause of the fire and the financial resources of the boat owners.

Families of 32 of the victims and one surviving crew member have filed claims against the Fritzler family trust and the boat company, Truth Aquatics. The Fritzlers and the company in turn have filed a legal claim to shield them from damages under a maritime law that limits liability for vessel owners.

Attorney Russell Brown, who represents the Fritzlers and made the disclosures in court papers, did not return a phone call or email seeking comment.

Brown said in a report filed Friday that a federal grand jury in Los Angeles issued subpoenas to the Fritzlers and Truth Aquatics Inc. on Sept. 11 and 18 seeking records on the boat and communications related to its safety operation.

He also revealed that Boylan met with prosecutors in a meeting held routinely when “the government has concluded that it has sufficient evidence to bring criminal charges.” He said “an indictment, or indictments, will be forthcoming.”

Federal investigators are still working to complete what’s known as an origin and cause report, which will rule if the fire was accidental, incendiary — meaning it was deliberately set — or undetermined. Authorities have said there is no indication the fire was arson.

The five-person NTSB will hold an Oct. 20 meeting to vote on the safety investigation’s findings, as well as the blaze’s probable cause and any potential recommendations.

An NTSB official has cited how difficult it was to reach an escape hatch in the Conception’s bunk room, a design that has routinely met regulations. Coast Guard records show the boat had passed its two most recent safety inspections without violations.

The NTSB is a federal regulatory agency but it has no enforcement powers and can only submit its suggestions to bodies like the Federal Aviation Administration or the Coast Guard, which have repeatedly rejected some of the board’s safety recommendations.

The Coast Guard has issued additional safety recommendations in the wake of the tragedy, such as limiting the unsupervised charging of lithium-ion batteries and the use of power strips and extension cords.