ATF investigators determined that the fire originated in the upper level of the engine room, portside aft. A paint locker was located in the area of origin, with various combustible materials stored both inside and outside the locker. Interviews with the vessel’s engineer revealed that a boot warmer had been plugged into an extension cord a few feet from the paint locker.
The boot warmer was stacked on a plastic trash can, and remnants of its control switch showed it was in the “on” position. After the accident, the extension cord’s insulation and plug were found burned down to the copper wiring. Additionally, the 30-amp breaker associated with the receptacle was found in the tripped position.
Breakers can trip due to overloaded circuits, shorts, or electrical faults. An electrical fault—such as a loose, broken, or frayed wire—within the plug or near the boot warmer could have caused excessive resistive heating, which can produce sufficient heat to ignite nearby combustibles. However, due to the extent of the fire damage, the exact ignition source and cause could not be determined.
Once the ignition source was produced, combustible materials in and around the paint locker, including paint cans and the plastic trash can, caught fire. These materials provided a path for the fire to spread to the port side of the engine room, aft.
Source: https://safety4sea.com/wp-content/uploads/2026/01/NTSB-MIR2601-2026_01.pdf