A historic military shell and grenade located in a Palo Alto home on Thursday afternoon prompted an investigation by the Santa Clara County sheriff's bomb squad, which detonated the grenade hours after it was found, police said.

The discovery was made at a home in the 2300 block of South Court around 3:10 p.m., when a resident reported what they believed to be a World War II-era grenade and artillery shell while they cleaned a deceased relative's home in the company of an estate liquidator, according to a police press release. The resident took the items outside and cautiously placed them in the front yard.

Officers and the bomb squad responded to the scene, where residents in immediate proximity to the home were asked to evacuate out of an abundance of caution. The items were located in a den closet of the two-story residence, police Sgt. John Alaniz said.

By about 6 p.m., bomb squad members concluded that military shell wasn't a threat, but believed the grenade was possibly still live after inspecting the items with their equipment. They took the grenade to an open area in Hoover Park where the squad dug an 18-inch-wide hole in the grassy area of the park far from the Cowper Street side and buried the grenade, then covered it with a mound of sandbags, according to Alaniz.

The bomb squad crew took cover behind a concrete handball wall as the device was detonated just before 7 p.m. A cloud of gray smoke emanated from the pile as a bomb squad member was heard yelling "fire in the hole!" A fragment of the black grenade's outer shell was left after the detonation, along with several other charred pieces of material.

There was no danger to about 20 people who were at the park and asked to leave the area prior to the detonation, or to homes near the open space, the department said. The park was closed for about 15 minutes.

No injuries were reported. Multiple police and fire units were on standby on South Court and at Hoover Park. Palo Alto Utilities employees responded as well to pinpoint gas lines in the area and Public Works crews provided sandbags used for the detonation.

Public access to South Court, a quiet, tree-lined street between North California Avenue and Oregon Avenue, was shut down for about three hours. The roadway reopened around 6 p.m.

Trevor Vaughan, a student who was returning from school in his family's car with his twin brother, Nathan, said they were greeted by police cars and the street was blocked off.

Mary Brodbeck, another neighbor on South Court, said residents couldn't bring their cars into the neighborhood.