More air and ground searchers are combing a rugged mountain area in southeast Wyoming for a single-engine plane carrying four people from Texas.

Albany County Undersheriff Rob DeBree says a U.S. Air Force helicopter is helping the search from the air and the ground search team has been bolstered to about 40 people.

The Wyoming Civil Air Patrol now has two planes in the search, which is focusing on Laramie Peak area about 60 miles southeast of Casper.

The Piper PA-32 aircraft was reported missing after it failed to land as scheduled Tuesday evening at Casper/Natrona County International Airport. It took off from Harrison County Airport in Marshall, Texas.

DeBree says the four people in the plane were traveling to Casper on business.

Officials have not released their names.