A recall has not been issued yet, but U.S. safety regulators are intensifying an investigation into complaints of stalling engines on Toyota Corollas and Matrix hatchbacks. The preliminary probe begun last November when the NHTSA received complaints for 2006 models, but the problem has been expanded to include almost 1.2 million 2005-2007 Corolla and Matrix cars.

The problem is being blamed on an improper coating on the engine control unit (ECU) circuit boards that lead to cracks in the coating. The NHTSA has received 163 complaints of stalling engines as of last week. It is unclear whether the investigation will lead to a recall.