TOKYO (Reuters) - Japan's Transport Minister said on Friday that he had directed Takata Corp to investigate its defective air bags, which have triggered massive recalls, adding the ministry was directly in touch with the auto safety equipment supplier over the issue.

The ministry usually relies on automakers themselves to report incidents and announce recalls, but in Takata's case, officials are talking directly to the supplier, underscoring the severity of the matter. "We are dealing with the matter strictly and directly ordering Takata to investigate (air bag) malfunctioning incidents and requesting information from them," Transport Minister Akihiro Ohta told a news briefing.

About 16 million cars fitted with Takata air bags have been recalled worldwide, with more than 10 million of those in the United States, where the Tokyo-based company faces a regulatory probe, a criminal investigation and more than 20 class-action lawsuits.

Executives from Takata and its major customer, Honda Motor Co, were called to testify at a United States Senate hearing on Thursday, where they apologised for injuries and deaths caused by air bags that exploded with too much force, shooting shrapnel into the vehicle. At least five deaths have been related to Takata's defective air bags, all in Honda vehicles.

Both regulators and Takata, which supplies one in five air bags globally, have yet to pinpoint why the parts are at risk.

The US National Highway Traffic Safety Administration called on Takata and five automakers this week to expand piecemeal regional recalls of driver-side air bags to cover the entire United States, as senators have urged.

Mr Ohta said he was asking automakers to determine if it was necessary in Japan to widen the recall of air bags to match those that were being expanded nationwide in the United States.