(CNN) -- Authorities evacuated a large section of a California park Friday after a passer-by spotted a pipe bomb -- the third such device planted in the park in the past two days, police said.
A resident discovered the suspicious, cylindrical device while walking through the 126-acre Newhall Park around noon (3 p.m. ET), police in Concord, California, said. Bomb squad investigators detonated the pipe bomb.
Police said the bomb's fuse had been ignited earlier, but it had not detonated.
Two other pipe bombs were found in the park Wednesday and detonated by the bomb squad, police said.
Police said Friday that they did not know who had placed the bombs and were investigating.