Aliso Canyon gas leak
The boundary of Southern California Gas Company property, where Aliso Canyon Storage Field is located, in the Porter Ranch neighbourhood of the of the San Fernando Valley region of Los Angeles, CaliforniaGetty Images

Southern California Gas Company has announced that it has temporarily controlled the flow of natural gas at a ruptured well at its Aliso Canyon storage facility in California. The leak at the company's underground gas well began on 23 October.

The company began drilling a relief well to stop the leak by plugging the leaking well at its base. It said it will continue to work towards permanently sealing the gas well, located in the neighbourhood of Porter Ranch outside Los Angeles.

"We have temporarily controlled the natural gas flow from the leaking well and begun the process of sealing the well and permanently stopping the leak," Jimmie Cho, the company's senior vice-president of gas operations, said in a statement. On 11 February, "the relief well intercepted the base of the leaking well, and the company began pumping heavy fluids to temporarily control the flow of gas out of the leaking well", the statement added.

A time-lapse video shot on infrared camera by the California Air Resources Board shows voluminous plumes of methane, not visible to the naked eye, disappear within minutes as crews began to control the gas flow.

Permanent sealing could occur over the next several days after cement is injected from the relief well into the leaking well at its base. A back-up relief well is also being drilled as a precautionary measure until the leak has been stopped permanently.

More than 150 million pounds of methane gas has leaked into the atmosphere in what is said to be one of the largest-ever methane leaks in the United States. The gas leak forced evacuation of over 1,000 people from nearby residential areas after people reported a pungent smell of the gas that triggered nausea and headaches.

Though the company claimed that the leak did not pose any threat to public safety, environmentalists warned methane can warm the atmosphere 80 times faster than the other greenhouse gas (carbon dioxide) in 20 years' time.