The Coast Guard has issued a safety warning for commercial boat operators, saying they should monitor the amount of unsupervised phone charging on their boats in the wake of a fire off the coast of California that killed 34 people.

USA Today reported that a preliminary report into the boat fire near Santa Cruz Island could come as soon as Thursday, according to the the National Transportation Safety Board. While the report will likely not include a cause, it will examine how batteries and electronics were stored.

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The Coast Guard urged those operating a boat to "reduce potential fire hazards and consider limiting the unsupervised charging of lithium-ion batteries and extensive use of power strips and extension cords," the bulletin said.

The Coast Guard also cautioned boat operators to ensure that their firefighting materials work and that emergency escapes are easier to find and are effective. It also encouraged boat operators to make sure the crew understands what to do in an emergency, according to USA Today.

The last body of the 34 victims was recovered on Wednesday. The dive boat caught fire and sank on Labor Day.