BOISE, Idaho (AP) — Emergency crews responded Sunday after witnesses reported two planes collided during a weekend air show at a military base in western Idaho.

The Mountain Home Air Force Base said in a social media post that it was locked down following the unspecified incident during the Gunfighter Skies Air Show. Responders were on the scene and an investigation was underway.

Multiple witnesses reported two planes crashed, and videos posted online showed four parachutes opening in the sky as the aircraft plummet to the ground near the base about 50 miles (80 kilometers) south of Boise.

No other information was immediately available, said a person who answered the phone at the 366th Fighter Wing public affairs office.

Organizers said the popular air show that includes flying demonstrations and parachute jumps is a celebration of aviation history and a look at modern military capabilities. The U.S. Air Force Thunderbirds headlined the show both days.

The National Weather Service reported good visibility and winds gusting up to 29 mph (47 kph) around the time of the crash.