Thieves made off with half of the Unkillable Human over the weekend.

Someone took the silhouette portion of the two-part Unkillable Human sculpture on the North Shore portion of the Three Rivers Heritage Trail. The 7-foot-high iron sculpture, created by artist Frederick Franck, was half of the installation that's accompanied by a granite tablet describing the sculptor's inspiration for the piece, which "came about on my return from Hiroshima, where burned into a concrete wall I saw the shadow of the fellow human evaporated the moment the Bomb struck. Through the empty negative - mere flames of steel - one sees the Human rising like a Phoenix from its ashes."

The sculpture was most likely stolen Saturday evening, according to a release from Friends of the Riverfront. The organization received many calls and messages from concerned users of the trail.

Friends of the Riverfront officials believe the sculpture was stolen for artistic value. Mr. Franck's work has gone up in value since his death in 2006, and similar pieces have sold for $40,000. In a scrap yard, the sculpture would be worth about $45, said Tom Baxter, executive director of Friends of the Riverfront.

Friends of the Riverfront asked that anyone with information call 412-488-0212 or e-mail Friends of the Riverfront at friends@friendsoftheriverfront.org.