One man killed, after his motorcycle leaves the southbound Highway 151 roadway in San Antonio, and crashes.

Authorities are investigating a fatal motorcycle crash that happened just after midnight Thursday on the far west side of San Antonio.

Police said an unidentified man was riding his Harley Davidson southbound on Highway 151, near Rodgers Road and Military Drive, when he failed to negotiate the curve of the highway and drove the motorcycle off the roadway.

According to the San Antonio Police Department, the man was not wearing a helmet when he was thrown from the bike. Officers said the victim died as a result of his injuries.

Police said they do not know if alcohol was a factor in the wreck.

No other vehicles were involved.