The National Highway Traffic Safety Administration said on Sunday that it will open an investigation into complaints that two Nissan Motors recalls have failed to handle an issue with front-seat air bag sensors.

The probe covers about 990,000 vehicles in the U.S. that were called back in 2013 and 2014, according to a report by the Associated Press.

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

The probe involves a computer software issue that may not detect when an adult is in the passenger seat. When that occurs, the air bags won't inflate properly, according to Time. Sensors in the seats can tell if a child is sitting there, but if they do, the air bags are turned off since they can harm a small child.

The NHTSA said 124 people have complained about the issue so far, even after repairs were made, according to documents posted on Sunday.

"The majority of the complaints allege the passenger air bag status light stays on for adult front passengers. Some of the complaints state the dealers have made multiple repairs but the problem still persists," NHTSA said, according to The Detroit News.

One complaint was filed with the NHTSA back in May by an owner of a Pathfinder that the vehicle had been taken to a dealership four times for two different recalls. The indicator light showed the air bag is turned off still remained illuminated despite the fact that an adult was 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 unidentified person in the complaint.

The safety administration said to the AP that it opened a "recall query" to examine the effectiveness of the software update.

Nissan said in a statement to AP that the repairs took care of any issues and that additional measures to help dealers handle customer concerns were not linked to the recalls.

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

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