WASHINGTON – The government has opened an investigation of more than 1.2 million General Motors Corp. pickup trucks and sport utility vehicles in 21 states, including Maine, amid questions about the vehicles’ antilock brakes.

The National Highway Traffic Safety Administration said Monday that stopping distances may increase when the brakes are applied at speeds of under 10 mph because of the build-up of corrosion.

NHTSA has reported nearly two dozen crashes, including one that involved six vehicles and four injuries because of the problem. There have been no fatalities associated with the braking issue.

The investigation involves 1.27 million GM trucks and SUVs from the 1999-2002 model years.