Mexico ? Mexican and U.S. authorities were searching Tuesday for a small plane that disappeared while carrying the U.S. and Mexican heads of the International Boundary and Water Commission.

Mexico’s Foreign Relations Department said in a statement late Tuesday that search crews from the two nations have been combing both sides of the border near the town of Ojinaga, across the border from Presidio, Texas.

It said the swelling of the Conchos and Bravo rivers have made the search difficult.

Earlier Tuesday, Chihuahua state Gov. Jose Reyes Baeza Reyes told reporters in Ojinaga that U.S. investigators had located the plane and that all four passengers had died in a crash. His press office later retracted his statement and said the search for the plane continued.