A 71-year-old motorcyclist remains in serious condition following a hit-and-run collision Sunday afternoon on Kamehameha Highway near Acacia Road in Pearl City, according to the Honolulu Police Department.

Police say the motorcyclist was traveling westbound on Kamehameha Highway around 3:20 p.m. when he lost control of his vehicle and was ejected onto the roadway. An unidentified motorist then struck the man and continued westbound without stopping to render aid or provide information.

Emergency Medical Services transported the motorcyclist to a nearby hospital. Police confirmed he was not wearing a helmet at the time of the crash.

It remains unclear whether speed, drugs or alcohol contributed to the incident.

Authorities are urging anyone with information about the collision or the unidentified driver to contact the Honolulu Police Department’s Traffic Division at (808) 723-3413.

The investigation is ongoing.