A grenade was found on Locust Street near Fern Avenue in Onset Sunday evening, causing the evacuation of residents from homes in the area and closing surrounding streets.

The Massachusetts State Police Hazardous Device Unit determined that the grenade was inert, said Onset Fire Chief Howard Andersen.

Wareham Police and the Onset Fire Department responded to the incident at approximately 6:50 p.m. and assisted with the evacuations and closures. Residents were allowed back into their homes and streets were reopened around 8:50 p.m.

The grenade "actually had no explosive powder in it, and it looked like it had been in the water for a very, very long time," said Jennifer Mieth, spokesperson for the office of the State Fire Marshal. She said it was unclear how the grenade ended up on Locust Street.