Detectives are looking for whoever threw what appeared to be a grenade out of a moving car Friday along a busy road in Riverside, Southampton police said Monday in asking for the public's help.

The green, cylinder-like object was lobbed out near Best Price Auto, 454 Riverleigh Ave., about 2 p.m. Friday, and it landed on the shoulder of the road, police said.

Employees at the store saw a motorist throwing the object from a dark-colored car and called 911, Det. Sgt. Lisa Costa said.

"It didn't appear to be an antique," Costa said of the device.

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Nearby workers and residents were evacuated as authorities treated the object as a live grenade, police said.

Riverleigh Avenue between Ludlam Avenue and the Riverside traffic circle was shut down until 7 p.m. while Suffolk County police arson and emergency services officers removed the object so it could be destroyed off site, Southampton police said. Flanders ambulance also responded, police said.

Costa said detectives are trying to determine if the auto repair shop was the target. "The owner said there were no unhappy customers," she said.

It is not clear if the device was live, but the investigation continues, police said. Anyone with information may call Southampton Town detectives at 631-702-2230.