Though they can't identify a specific worker as the culprit in the March 11 fire that destroyed that under-construction condo development in Mission Bay, the investigator's report into the blaze concludes that the blaze was most likely caused by leftover embers or byproducts from welding work happening that day between the top floor and the roof.

As Bay City News reports, the fire began in the southeast section of the building near where workers "had been installing and welding a perimeter guardrail on the top of the building" that day. The welding and grinding of steel end-caps of the rail was going on over bare plywood, and the investigator concludes:

I am unable to eliminate an event involving either the by-products of welding coming into contact with the bare wood roof materials, or embers resulting from grinding the steel end-caps of the steel hand-rail coming into contact with the bare wood roofing materials as the ignition source.

Construction crews left the site around 3:10 p.m. and it wasn't for another 2 hours that a neighbor reported seeing a "small flame" and smoke near the roof of the building.

A preliminary investigation had already ruled the fire accidental, and now the report confirms this. It seems likely, though, that Suffolk Construction Co., the contractor, will have to bear the insurance responsibility, though they may try to point the finger at a subcontractor, of which there were many on the site that day.

[BCN/Appeal]
[Chron]