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

Videos posted online showed the two planes getting tangled together in midair before four parachutes opened in the sky as the planes plummeted to the ground.

All four air crew safely ejected from the US Navy EA18-G jets, Cmdr. Amelia Umayam, a spokesperson for Naval Air Forces, US Pacific Fleet, told CBS News in a statement.

The EA-18G Growlers were assigned to Electronic Attack Squadron 129 from Whidbey Island, Washington, according to Umayam. Each unit costs approximately $67 million, according to the US Navy.

No other information was immediately available, the 366th Fighter Wing public affairs office said.

The popular air show is a celebration of aviation history and a look at modern military capabilities and includes flying demonstrations and parachute jumps, according to the event's organizers. The Thunderbirds, the US Air Force's flight demonstration squadron, were scheduled to headline the show both days.

The air base later said it secured the area where the crash occurred and canceled the rest of the show for Sunday.