A Fisherman's Wharf street performer's act, apparently devised to alarm onlookers, instead riled up police, who closed a block of Jefferson Street believing that the man might have been juggling a live hand grenade.

The man, police said, was seen tossing around what appeared to be an authentic hand grenade at about 5 p.m. Saturday on the 300 block of Jefferson Street near Jones Street, an area popular with tourists.

Officers detained the performer, confiscated the grenade and quickly determined that it was merely a replica. The block reopened about an hour after.

Police on Sunday did not identify the performer or say whether he could face charges.