Chain-reaction crashes are not for cars alone. Four bicyclists were injured in such a collision Saturday in the Potomac area of Montgomery County, authorities said.

One cyclist went down about 8:30 a.m. in the 10300 block of Glen Road, leading to injuries to three others, said Pete Piringer, the county fire and rescue spokesman.

One of the men was seriously injured. The others had bumps, bruises and abrasions, Piringer said. All were taken to hospitals.

In an earlier recreation-related incident in Montgomery, three people were injured in separate incidents Friday on the rugged Billy Goat Trail along the Potomac River. One was hoisted out by helicopter, Piringer said.