The National Highway Traffic Safety Administration has opened a probe to assess the effectiveness of General Motors Co.'s vehicle recall in 2014 over faulty seat belts, according to a May 28 notice from the agency.

The carmaker in 2014 recalled certain Outlook, Acadia, Enclave and Traverse models following reports of the front outboard safety belts detaching from the seat-mounted pre-tensioner. The remedy was to inspect for signs of damage and replace pre-tensioners as needed.

However, the NHTSA said its Office of Defects Investigation still received four complaints about the issue even after the recall remedy had been applied.

The agency then decided to open a recall query to assess the effectiveness of the 2014 recall.