ST. PAUL — The number of motorcycle fatalities on Minnesota roads in 2015 is now at 11 — the highest number for this point in the year since records began in 1994, according to the Minnesota Department of Public Safety.

The total rose this month when four motorcyclists died in separate crashes within four days.

“With an early spring, we have had more riders on the road,” Lt. Tiffani Nielson with the State Patrol said in a statement Thursday. “Riders and motorists should be alert and take steps to preventing crashes.”

The State Patrol said rider error appears to have played a factor in several of this year’s crashes. Preliminary reports show speed contributed to four of the crashes.

Seven of the 11 riders were not wearing helmets, and two of those killed were passengers, the department of safety said.