A motorcyclist was taken to a hospital after he was involved in a single-vehicle crash in Waialua.

The crash occurred at an S-turn on Kaukonahua Road shortly before 10 p.m. Thursday.

Lt. James Slayter of the Honolulu Police Department’s Traffic Division said a 34-year-old Waipahu man was traveling westbound on a black Yamaha motorcycle when he lost control and struck a guardrail.

Upon impact, he was thrown into a gulley in a pineapple field.

Emergency Medical Services treated and transported him in critical condition to a hospital.

His condition has been upgraded to serious condition.

Slayter said he was wearing a helmet at the time of the crash.

Speed is a possible factor. It is unknown at this time whether alcohol was involved.

The investigation is ongoing.