U.S. auto safety regulators have opened an investigation into complaints that General Motors vehicles equipped with certain V8 engines, including its best-selling Silverado, can seize up without warning.

The National Highway Traffic Safety Administration’s Office of Defects Investigation has begun looking into engine failures involving an estimated 877,710 vehicles from GM. The vehicles are full-sized trucks and SUVs equipped with the 6.2-liter L87 V8 engine.

NHTSA said it was investigating an estimated 877,710 vehicles after receiving 39 complaints from users of GM vehicles equipped with L87 V-8 engines.

US auto safety regulators have opened an investigation into complaints that General Motors vehicles equipped with certain V8 engines, including its best-selling Silverado, can seize up without warning.