Shares in Japanese auto parts firm Takata plunged nearly 17 percent in Tokyo on Monday following calls for a criminal investigation into an airbag defect that has been linked to at least four deaths.

The firm sank 16.87 percent to close at 1,177.0 yen after two US senators on Friday called for a criminal probe, and as the New York Times reported that Takata covered up the fault.

The embattled firm — whose shares have lost about 60 percent since the start of the year — on Thursday issued a warning of a bigger-than-expected annual loss, as it faces lawsuits and regulatory probes.

Questions continue to mount over airbag defects linked to the deaths in the US and dozens of injuries.

Millions of vehicles produced by some of the largest automakers, including Toyota and General Motors, are being recalled because of the risk that an airbag could improperly inflate and rupture, potentially firing deadly shrapnel at the occupants.

The firm has largely shied away from commenting on the scandal, saying little as it announced its financial results in Tokyo Thursday.

Takata was founded in 1933 as a textile company and evolved into an automotive parts giant that started selling airbags in the 1980s.

It has dozens of plants and offices in 20 countries, including the United States, China and Mexico.

The airbag division accounts for about 40 percent of its total revenue, which amounted to 556.99 billion yen ($4.88 billion) last fiscal year.