Media playback is unsupported on your device Media caption LA residents like Erin Brockovich speak out about methane leak

The company behind a massive gas leak in California has denied it is responsible for an environmental catastrophe.

SoCal Gas said it was deeply sorry for what happened and is working to stop the leak, though it could take weeks.

It says the gas being pumped into the atmosphere, which includes methane, is not a threat to public safety.

"I wouldn't term it that," Mike Mizrahi of SoCal Gas told the BBC, when asked if it was an environmental catastrophe.

The leak began in October in a vast underground storage field in Porter Ranch, on the outskirts of Los Angeles.

The company hopes to fix it by late March.

On Wednesday California Governor Jerry Brown declared a state of emergency and called for "all necessary and viable actions" to stop it.

More than 10,000 people have been moved from their homes and many people have reported nausea and headaches.

A further estimated 7,000 are now in the evacuation process, according to SoCal Gas.

How did the leak start?

A broken injection-well pipe about 500 ft (152.4m) below the surface is thought to be to blame.

Why hasn't it been fixed?

Repair work has been slow due to the nature of the leak.

What might the environmental effect be?

Methane - the main component of natural gas - is a very strong greenhouse gas, capable of trapping solar radiation in the atmosphere.

The BBC's Matt McGrath says the large amounts of powerful gas that are leaking could have a significant impact on climate change.

What's behind California's 'health catastrophe'?

"We're anticipating by late February to late March somewhere in that time frame we will be able to intercept the well at about 8700 feet" and stop the leak, Mr Mizrahi said.

He said they regret the leak but "can't verify the amount of gas" that has come from it.

"We feel terrible about this. These are our neighbours and our apology is sincere and heartfelt and we are doing everything we can to meet the needs of our residents."

Image copyright AP Image caption SoCal said it was deeply sorry

At the scene - James Cook, BBC News, Porter Ranch

The stench comes and goes but when the wind is blowing in the wrong direction, the fumes can be overwhelming.

Residents of this smart, gated-community about 30 minutes from downtown Los Angeles are literally sick of it.

SoCal Gas insists the gas leaking from Aliso Canyon in the hills above the town does not pose an "imminent threat to public safety," but people here are still worried - about their health and the impact on the environment.

Residents have complained of nausea, nosebleeds and worse, with some saying they were so sick they had to go to hospital. They point out cars, outdoor furniture and houses which have been marked with brown, oily spots.

There is a feeling here that the leak has not been taken as seriously as other environmental disasters because the gases are invisible to the naked eye.

The declaration of a state of emergency may be welcome but here in Los Angeles many people say it has come far too late.

Media playback is unsupported on your device Media caption The 'happy-go-lucky' community turned into a ghost town

Tim O'Connor, a lawyer with the Environmental Defense Fund, has called it "an environmental and public health catastrophe," said .

"In terms of timelines this is going to surpass the gulf oil problem by a mile."

It's the same amount of pollution as 4.5 million cars put out every day, he said.