Toyota is investigating complaints that its Prius hybrid cars are stalling in the United States, company officials said Tuesday.

A few owners of the 2004 and 2005 Prius models are saying their cars stalled, Toyota Motor Sales U.S.A. Inc. said in a statement without elaborating.

Hybrid vehicles deliver good mileage by switching between a gasoline engine and an electric motor. Toyota Motor Corp. leads the industry in hybrids, with cumulative global sales of 381,500.