I think the main issue is any potential fire, there are many old...

I think the main issue is any potential fire, there are many old burning mines on the coast that self combusted.

Pratically speaking the explosion would likely to have been where one of the crews were working and they hit a pocket of gas. It must have been a sudden event for the gas leak as they use sophisticated gas metering these days.

Does not look good, very sad time and my heart goes out to the familys, friends and collegues.