(CNN) -- The mayor of Piedras Negras, Mexico, and the secretary of public works and transportation in the state of Coahuila were killed in a plane crash Wednesday, the government-run Notimex news agency reported. There was an explosion on the airplane while flying over the Escondido River, Notimex said. The news agency identified the men as Mayor Jose Manuel Maldonado and Coahuila official Horacio del Bosque Davila. The pilot, who was not identified, also was presumed dead. Coahuila Gov. Humberto Moreira Valdes confirmed the deaths, Notimex said. The aircraft, which took off from Piedras Negras, plunged into the Fragua Dam, the news agency said. Notimex said the aircraft was a Piper Cheyenne, a twin-engine turboprop plane. Patricia Rivero of the Coahuila's prosecutors office told CNN officials were still at the scene and she did not have further information.
Explosion occurred aboard plane before crash, government-run news agency reports . Piedras Negras mayor and Coahuila secretary of public works and transportation were killed . The pilot, who was unidentified, also was presumed dead . Crash is still under investigation, official said Wednesday .