The National Highway Traffic Safety Administration (NHTSA) has started investigations into manual transmission issues on new Ford Mustangs and fuel leaks reported on diesel Volkswagen Jetta sedans.

The agency, part of the federal Department of Transportation , said it had opened a preliminary investigation into 26,000 2011-2012 Mustangs after receiving 32 complaints alleging an “unexpected inability to shift into gear”.

Some complaints said incidents occurred while merging into high-speed traffic while others said incidents occurred while turning left across oncoming traffic.

The NHTSA also said it’s investigating 40,000 2011 Jetta TDI vehicles after it received seven complaints alleging leakage from the fuel line to the fuel injector. One similar complaint was received regarding a Volkswagen Golf also equipped with a two-litre TDI engine, the agency said.

Media reports said that Ford was aware of the investigation and will fully cooperate with the review. A VW spokesman was unavailable for comment.