LOS ANGELES — A blowout at a natural gas well that leaked uncontrollably for 16 weeks and drove thousands of residents from their Los Angeles homes was plugged Thursday, a utility said.

While the well still needs to be permanently sealed with cement and inspected by state regulators, the announcement by Southern California Gas Co. marked the first time the massive leak has been under control since it was reported Oct. 23.

“We’ve achieved control of the well today,” said Jimmie Cho, a SoCalGas senior vice president. He said he was very confident they would complete the job.

The leak is expected to cost the company, a division of Sempra Energy, $250 million to $300 million, according to a filing with the Securities and Exchange Commission.

That figure could climb much higher because it only accounts for costs of capping the well, lost gas and relocating families. It does not include potential damages from more than 65 lawsuits, penalties from government agencies and expenses to mitigate pollution, which the company noted could be significant.

If the plug holds and all goes according to plan to seal the well, the upscale Porter Ranch community in the San Fernando Valley could begin to return to normalcy after schools were closed and 6,400 families were uprooted as they complained of headaches, nausea, nosebleeds and other symptoms as an intermittent stench wafted through the area.

Public health officials blamed their woes on an odorant added to gas so it can be detected and have said they don’t expect long-term health impacts.

Vicky Walker, who lives close to the facility, said the smell was particularly strong the past few nights but wasn’t noticeable Thursday afternoon.

She spent three to four nights a week in a hotel after developing a cough, but returned regularly to work from her home office. But she gained five pounds as she stayed inside as much as possible and stopped walking her dog.