Displays of Takata Corp are pictured at a showroom for vehicles in Tokyo Nov. 5, 2014. REUTERS/TORU HANAI

(Reuters) - Japan's Takata Corp (7312.T) is the subject of a U.S. criminal investigation over defective car air bags that have been linked to five deaths, a company spokesman said on Thursday.

A federal grand jury in New York has subpoenaed Takata's unit in the United States to produce documents on the air bag defects, the Tokyo-based spokesman said.

Separately, the U.S. Senate commerce committee scheduled a hearing next Thursday to solicit testimony from Takata executives on air bag defects, as well as from officials of the National Highway Traffic Safety Administration on the recall process.

Defective Takata air bag inflators have been found to explode with dangerous force in accidents, sending shards of metal into the vehicle.

An investigation by U.S. prosecutors in Manhattan into the Japanese safety-parts maker had been previously reported, but Thursday's statement is the first indication that a seated grand jury was seeking evidence.

Takata disclosed the probe in a closed-door meeting with financial analysts, according to an account from one participant.

The participant said Takata had told the analysts it was not considering adding production lines to make replacement air bag inflators, explosive devices that allow air bags to inflate in a fraction of a second during a crash.

Takata's U.S. spokesman Alby Berman told Automotive News, however, that the company is preparing to build two new production lines at its plant in Monclova, Mexico, with a January startup planned.

Berman did not respond immediately to a Reuters request for comment.

In Japan, Takata told analysts that it was making "constant improvements" to the chemical compound used in its inflators, but said they were not related to any defects or accidents.

NHTSA has also issued a special order demanding documents and other evidence on air bag defects. Takata has until Dec. 1 to comply.

Since 2000, Takata has made more than 100 million inflators, according to industry estimates and company data. Since 2008, more than 17 million cars equipped with Takata air bags have been recalled, including more than 11 million in the United States.

In a statement posted Thursday on the company's website, Chief Executive Officer Shigehisa Takada apologized to customers and shareholders for the company's problems: "Our whole company will strengthen our quality management structure and work to prevent an incident from occurring again," Takada said.

Separately, Takata disputed a recent New York Times report that it had failed to tell federal regulators that it had found signs of air bag defects in secret tests in 2004 in Michigan.

The company said it believed the Nov. 6 story "was based on serious misunderstandings of the facts." It said it was testing air bags for tears to cushions in their modules, not for inflator ruptures, as reported.

The fifth fatality linked to Takata air bags, and the first outside the United States, was disclosed earlier on Thursday. Honda Motor Co Ltd (7267.T) said a driver in Malaysia had died in July after being hit by shrapnel from a Takata air bag.

All five deaths have been in Honda cars. The Japanese carmaker, Takata's biggest customer, widened its recall for the defective air bags by 170,000 more vehicles globally, taking the total to nearly 10 million.