The transport ministry said Wednesday a Takata Corp. air bag ruptured in a model not covered by existing recalls, suggesting automakers may have to expand safety campaigns to replace the devices linked to five deaths.

The air bag from a 2003 car ruptured during testing of devices from scrapped vehicles in Gifu Prefecture, Masato Sahashi, a ministry official, told reporters at a briefing in Tokyo. The Nov. 6 incident may result in a recall once the reason for the malfunction is determined, Sahashi said, declining to name the automaker or model.

Regulators in Japan are stepping up pressure on Takata over its air bags, which have been linked to at least four deaths in the U.S. and a fatal accident in Malaysia. The scrutiny adds to investigations of Takata and its customers including Honda Motor Co. in the U.S., where the National Highway Traffic Safety Administration is trying to determine why the devices are deploying with too much force and shooting metal shrapnel at passengers.

The Takata air bag was the seventh to have ruptured during tests in Japan, where 700,000 of the devices were evaluated in 2012 and 2013, Sahashi said. The previous six were in cars included in recalls, he said.

The ministry said yesterday it was forming a group to oversee recalls of vehicles equipped with the devices, and that it was aware of four air-bag ruptures in vehicles that were in use. There were no injuries because the front passenger seats were not occupied when the air bags deployed.

Takata spokeswoman Kikko Takai couldn't immediately comment on the transport ministry briefing when contacted.