DETROIT (AP) — U.S. safety regulators are investigating complaints that two Nissan recalls didn't go far enough to fix a problem with front-seat air bag seat sensors.

The probe covers nearly 990,000 vehicles in the U.S. that were recalled in 2013 and last year because computer software may not detect an adult in the passenger seat. If that happens, the air bags won't inflate. Cars have sensors in the seats that can tell if a child is sitting there. The air bags are then turned off because they can harm a small child.

The recall affects the Altima midsize car, Leaf electric car, Pathfinder SUV and Sentra compact models from the 2013 and 2014 model years, as well as the NV200 Taxi van and Infiniti JX35 SUV from 2013. Also covered are the Infiniti QX60 and Q50 SUVs from 2014.

The National Highway Traffic Safety Administration says 124 people have complained about the problem happening after repairs were made. Nissan maintains the fixes took care of the problem.

In documents posted Sunday, NHTSA said Nissan and Infiniti owners complained that after getting recall repairs, the passenger air bag status light stays on, indicating the air bag is turned off even though an adult is sitting in the seat.

In one complaint filed in May, the owner of a Pathfinder told NHTSA that the vehicle had been taken to a dealership four times for two different recalls. But the indicator light showing the air bag is turned off remains illuminated, even though an adult is sitting in the seat.

"I feel that this is a safety issue in spite of being told by the service department that the air bag will deploy even if it is off," wrote the person, who was not identified in the complaint.

The safety agency said it has opened a "recall query" to assess the effectiveness of the recall fix, which was a software update.

In a statement, Nissan said it believes the update took care of the problem. The company said it took additional steps to help dealers address customer concerns that weren't related to the recalls.

The original recalls also covered about 60,000 vehicles in Canada and other countries.