State Police say speed and impairment may be to blame for a fatal motorcycle wreck late Sunday on Interstate 12 east of Hammond.

William Wilbert, 46, of Hammond, was driving a 2005 Harley-Davidson east on I-12 near Airport Road sometime before 10:20 p.m. when, for reasons under investigation, he ran into the back of a 1994 Chevrolet truck driven by 31-year-old Wayne McGary, of Ponchatoula, Trooper Greg Marchand said in a news release Monday.

Wilbert was speeding, and when he struck the Chevrolet, he lost control and was thrown from the motorcycle, Marchand said. The Tangipahoa Parish Coroner’s Office pronounced Wilbert dead at the scene.

Wilbert was wearing a Department of Transportation-approved helmet. Troopers suspect impairment, and toxicology results are pending, Marchand said.

McGary and his front seat passenger, 64-year-old James Wright, of Independence, were restrained and not injured. McGary voluntarily submitted to a breath test, which indicated no alcohol was in his system, Marchand said.

The crash remains under investigation.