Police say they're investigating reports remains of small explosive devices were found at two natural gas drilling sites in northeastern Pennsylvania.
Shell Oil Co. spokeswoman Kelly OpDeWeegh said in an email Thursday the company contacted state police on April 12 after "charred debris" was found at an inactive drill site in Tioga County.
Shell also informed authorities of a possibly similar finding on a different pad on March 21.
State police spokeswoman Maria Finn says there are no signs people or drilling operations were in any danger. She says the investigation into "possible components associated with small explosive devices" is ongoing.
Houston-based Shell says the FBI also is involved.