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The huge shock collapsed hundreds of buildings in downtown San Francisco; water and gas mains tore open, causing a huge fire.

Eventually, the methane reaches local gas mains where it’s metered out to customers.

“There is work in the vicinity of the house to replace a gas main. Based on what we know at this time, that work is unrelated to the incident,” Tracy said.

They said were in the process of obtaining the necessary permissions for replacing the gas mains when the leak was picked up by satellite.

Gas company Wales & West Utilities said it has received no reports of the smell of gas prior to the explosion and that the blast was unrelated to the gas mains network.