The Coast Guard is saying the fire was initiated by a broken fuel line for one of the diesels, and the fuel 'came in contact' with a 'hot surface.' I don't know what type of fuel they were using at that moment. It could have been diesel or lower grade fuel oil which is what they burn when not in ports and in same cases in the territorial waters of certain nations. But one thing I do know is the flash point for both diesel fuel and fuel oils is not that high, thus the 'hot surface' didn't need to be especially hot. 120-200 degree range would do it.