About 100 people were briefly evacuated from the Monte Rio Beach on the Russian River after a 5-inch-long pipe bomb was discovered in the beach parking lot late Saturday morning, Monte Rio Fire Chief Steve Baxman said.

A local man out walking his dog spotted the bomb on the ground underneath the bridge that carries Bohemian Highway over the river and called Baxman at home, the chief said.

Monte Rio firefighters responded at 10:56 a.m. and called the Sonoma County Sheriff’s Office. Deputies evacuated the beach and closed the bridge to traffic.

“We were being safe,” Baxman said.

The bomb was fashioned out of a roughly three-quarter-inch diameter metal pipe with a fuse about 5 inches long sticking out of one end, he said. Baxman speculated that the homemade device could have been intended for a Fourth of July explosion.

The sheriff’s bomb squad disarmed the device, Baxman said, and the beach was reopened about 12:30 p.m.