PHOENIX - The Arizona Department of Public Safety said a Valley man is dead after being struck by a vehicle after losing control of his motorcycle on the I-10 transition ramp from westbound Loop 202 Red Mountain.

The motorcycle rider, a Glendale man in his 30s, was struck by at least one vehicle after he fell onto the roadway during the initial crash around 2:30 a.m. Sunday, according to DPS.

The rider was not wearing a helmet and was pronounced dead on the scene of the accident, DPS said.

Investigators are working to determine the cause of the collision and whether more than one vehicle struck the motorcycle after the initial crash, DPS said. It is unclear if the motorcyclist was impaired.

No other information about the crash was given.