Texas ? The wreckage of a plane carrying Mexican and U.S. officials checking on border-area flooding was found Wednesday in a mountainous area two days after it disappeared, and officials said all four people aboard were killed.

The dead included the leaders of the U.S. and Mexican sections of the International Boundary Waters Commission, the executive director of an El Paso-area government council and the pilot, the commission said in a written statement.

The plane was reported missing after it did not land on time Monday in Presidio, a border town about 250 miles southeast of El Paso. The wreckage was spotted by air shortly after noon in Mexico’s Sierra Madre mountains. The cause of the crash isn’t known, and it’s unclear what agency will lead the investigation.

Killed were IBWC leaders Carlos Marin of El Paso and Arturo Herrera of Ciudad Juarez, Mexico. Also on board were Jake Brisbin Jr. of the Rio Grande Council of Government and Matthew Peter Juneau, the pilot of the chartered Cessna 421, the IBWC said.