According to a report from the Detroit Free Press, Ford has looked into the stems used on the majority of its vehicles and said it found a low rate of problems and no safety risks. However, the report says safety advocates claim any threat of sudden air loss in tires should be seen as serious enough to merit a recall.

The National Highway Traffic Safety Administration (NHTSA) launched a separate investigation in May looking into 23 million replacement valve stems manufactured by Shanghai Baolong Automotive Corp. in 2006. The agency has found 4,767 complaints related to those valve stems, including one fatal crash of a 1998 Ford Explorer following a tire failure, according to the Free Press report.

NHTSA’s investigation has looked into more than 1 million Ford cars from a variety of 2007 models and has found 37 complaints of bad valve stems, 23 of which had more than one bad stem on a vehicle and 11 instances where the air leaks were severe enough to damage the tire, the report said.