TOPPENISH, Wash. -

Authorities say a 22-year-old man has died after a flatbed trailer he was pulling with a small tractor came loose and pinned him in southern Washington.

Yakima County sheriff's Sgt. Chad Peterschick says David Alonso Gonzalez-Rebolledo died in the industrial accident around 12:30 p.m. Sunday in Toppenish on the Yakima Reservation. The name of Gonzalez-Rebolledo's employer hasn't been released.

Peterschick says it's unclear whether the 25-foot empty flatbed trailer dislodged when Gonzalez-Rebolledo hit a parked semitruck or if the force of the trailer coming loose pushed the tractor into it. The trailer went over the top of the tractor and fell on top of him.

The sheriff's office says the state Department of Labor & Industries will investigate any possible safety violations and the county coroner will conduct toxicology tests.