A 13-month investigation to pinpoint the cause of a dive boat fire that killed 34 people off the coast of California in 2019 was unable to establish a definitive cause of the blaze.

Cell phone chargers were suspected of starting the nighttime fire a deck above the sleeping quarters where 33 passengers and one crew died, but the 75-foot vessel, Conception, was too badly burned for the investigation to establish where and how the fire began.

The blaze was discovered by the captain and other crewmembers who were prevented from saving anyone when the paths to the sleeping quarters were blocked by the fire.

Investigators said certain requirements were not followed by the crew, including using a nighttime roving patrol, which might have saved lives. The vessel had smoke detectors in the sleeping quarters, but not the common areas where the fire is believed to have started.

Truth Aquatics, the Conception’s operator, had a good safety record, but investigators said that “complacency and a lack of imagination by the crew and the Coast Guard played a part in the death toll.”

You can read more in this Washington Post story.