A 19-year-old man was killed last night when his dirt bike collided head-on with another dirt bike in Calvert County, the county sheriff's department said.

The second dirt bike operator, also a 19-year-old man, was seriously injured in the collision, which occurred about 7:25 p.m. in the St. Leonard area of the county, about 40 miles southeast of Washington, the sheriff's department said.

Neither of the men was identified immediately, and it was not known why the vehicles ran into each other.

Sgt. David Allen of the sheriff's department described the vehicles involved as essentially small motorcycles. They have also been described as off-road motorcycles.

The crash occurred in a rural area on Williams Wharf Road, a two-lane thoroughfare near Broomes Island Road.

Operating dirt bikes on public roads in Calvert County is prohibited, but it continues, Allen said. "We do have a problem with this." Dirt bikes were banned from public streets in Baltimore in 2000 after crashes killed two young men.

The vehicles have become particularly popular among youths living in the rural communities on the edges of the Washington region. A woman living near where the crash occurred said she has seen children as young as 9 or 10 driving dirt bikes on the road.

Accidents involving the motorcycles have been common, but fatalities were described as rare.