Gov. Gavin Newsom’s administration has yet to release details about its $1 billion contract with a Chinese company hired to provide masks to combat the spread of the coronavirus — a deal that has drawn scrutiny over the company’s reported track record of selling defective products.

An official from the Newsom administration refused to provide state senators with a copy of the contract during a budget oversight hearing in Sacramento on Thursday, despite the state having already paid half the cost.

Christina Curry, chief deputy director of the state Office of Emergency Services, told senators via videoconference that disclosing all the specifics of its contract with the Chinese manufacturer BYD could disrupt the supply line of masks to the state.

“We have concerns about releasing too many details of it,” Curry said. “Our goal is to get the supply into California for the people who need it.”

She added, “We do intend to provide that when we have assurances that the supply is going to be arriving and with the requirements that we have set forth.”

The Office of Emergency Services hasn’t provided a timeline for when it will release the contract, which the governor has declared will provide the state with 200 million protective masks monthly to provide to hospital workers and others.

The deal came under scrutiny after Vice News reported that BYD, which stands for Build Your Dreams, has previously been blacklisted from some federal contracts because of concerns about the quality of its products.

BYD has no history of making medical protective gear, and it only recently retrofitted a factory to produce masks. The company’s subsidiaries specialize in manufacturing electric vehicles, including buses sold in the United States.

BYD did not respond to a Chronicle request for comment. Company spokesman Frank Girardot told the Associated Press that it “absolutely, 100%” complies with U.S. safety requirements.

Some California lawmakers have been asking for details of the BYD contract for more than a week.

State Sen. Holly Mitchell, a Los Angeles Democrat who chairs the Budget Committee, sent a letter to the Newsom administration requesting full details, including quality standards and price per mask.

“Under normal circumstances, the Legislature would have had more time to deliberate an expenditure of this magnitude and would have been allowed to thoroughly vet the details of the contract before proceeding,” Mitchell wrote.

On Thursday, Curry brushed off senators’ questions for more information, including a request for a public accounting of where masks will be sent. She said disclosing those details could threaten the state’s supply because such masks are now highly sought after.

Sen. Richard Pan, a Sacramento Democrat and physician, kept pressing.

“Since we’re a coequal branch, at least share that privately with the Legislature so we know,” Pan said. “Because we have to exercise our oversight function.”

Dustin Gardiner is a San Francisco Chronicle staff writer. Email: dustin.gardiner@sfchronicle.com Twitter: @dustingardiner