An enormous explosion just rocked San Bruno, California, a suburb just above San Francisco International Airport. Like, really big: A whole block is on fire with 200-foot flames. Six people are in critical condition. What the hell is going on?

Update: SFist, which is updating constantly on the fire, writes that most officials seem to be in agreement that the cause was a break in a natural gas line, though Pacific Gas and Electric hasn't yet confirmed that it was one of their pipes. Apparently locals are saying that they'd been complaining of a gas smell in the area.

Casualties are currently unknown, though local hospitals are operating under emergency triage conditions, and some reports are circulating of 911 calls from people trapped inside their homes. The surrounding area has been evacuated, and the fire is subsiding, though firefighters say the blaze will likely continue until morning.

The Red Cross is currently looking for blood donors—particularly of the universal donor-type O-negative. Locals can call 1-888-443-5722 for more information.

Here's another pic of the fire, courtesy, like the one up top, RodrigoBNO:

The Los Angeles Times, put together a Google Map of the fire's (huge) area:

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View San Bruno explosion fire in a larger map

And here are some AP photos of the blaze: