PALO ALTO (CBS-SF) – The Santa Clara County Sheriff’s bomb squad detonated an inert hand grenade Monday evening after it was discovered by construction workers at the Stanford Research Park in Palo Alto Monday afternoon, prompting evacuation and shelter-in-place orders, according to police.

Around 1:30 p.m. police received a report indicating that a construction worker had found a hand grenade about four feet underground while digging a trench outside an office building occupied by Stanford University Procurement at 3145 Porter Drive.

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The worker picked the grenade up, realized what it was and “hastily” threw the grenade to an open area near the roadway, according to police.

People at 3145 Porter Drive were evacuated while those at the adjacent address of 3155 Porter Drive were asked to shelter in place, according to police. The 3100 block was temporarily closed while a bomb squad investigated the device.

Police announced at 5:28 p.m. that the bomb squad had detonated the hand grenade. They determined it had been an old fragmentation device that was extremely decomposed, and did not contain any explosive material.

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The 3100 block of Porter Drive was closed to traffic for roughly four hours, according to police.

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