Police are seeking witnesses to a motorcycle crash in Chinatown Sunday night.

A 51-year-old Aiea man was taken in critical condition with head injuries to the Queen’s Medical Center after the crash about 7:45 p.m., police said.

Police said the man, who was not wearing a helmet, was traveling makai on Nuuanu Avenue before North King Street when the motorcycle veered left, fell to the ground and struck a curb. The rider was thrown from the motorcycle.

Police found no witnesses to the crash and urge anyone with information about it to call the HPD Traffic Division at 529-3499.