The noise from the exploding device could be heard several blocks away. There was no damage to any property and no one was hurt.

As of Monday afternoon police said no one had taken responsibility for leaving the

12-inch-long device in the park on the 6300 block of Moraga Avenue.

A woman walking her dog about 10:12 a.m. saw the bomb at the base of a tree along the left field foul line of the park's baseball diamond. The tree is one of several next to a chain link fence separating the spacious park from the Albertsons supermarket, Officer Murray Hoyle said.

Hoyle said police are not sure when the bomb was left in the park.

After police determined it was a real bomb, Moraga Avenue — the street closest to the bomb — was closed to cars and people. Pedestrian traffic was stopped on Mountain Boulevard, and employees at businesses on Mountain were told to move to other parts of their buildings, Hoyle said. There were no evacuations.

The Alameda County Sheriff's Department Bomb Squad was called to the park.

Deputies moved the bomb about 200 feet away from the tree to the center field area of the baseball diamond and detonated it at 12:10 p.m.

An Oakland police bomb sniffing dog then made a "protective sweep" of the park to ensure no other bombs had been left before the park was reopened.

The bomb finding was the second

Friday afternoon, two teenagers playing basketball on a court near the baseballdiamond got into a fight, and one of them brandished a knife.

An off-duty Berkeley police officer who happened to be nearby disarmed the knife-wielder and held him at gunpoint until police arrived to take the youth into custody. No one was injured.

Police and Crime Stoppers of Oakland are offering up to $2,500 for information leading to the arrest of whoever left the bomb. Anyone with information is asked to call police at 238-3426 or Crime Stoppers at 238-6946.