CUMBERLAND, Ind. -- A pipe bomb was detonated Sunday night after two were discovered at a Marion County park.

Police found that one of the bombs had already detonated and another was found in a duffel bag left in an open field at Lions Park, 6News' Ericka Flye reported.

There were no reports of injuries as crews caused the second bomb to explode, startling some neighbors.

"I just opened by back door to check on my dog and all of a sudden just boom, and I saw my dog actually come up from the ground," said neighbor Roxy Cole.

Investigators are not sure where the bombs came from or who left them there, but said they were looking for two men and two men in a black pickup truck and a gold sedan seen leaving the area before the bombs were found.