During the Commemorative Air Force Wings Over Dallas exhibition at Dallas Executive Airport, two historic warplanes collided in the air, on Saturday.

A Bell P-63 Kingcobra and a Boeing B-17 Flying Fortress both crashed, according to the Federal Aviation Administration, at around 1:20 pm. The airfield is located in the 5300 block of Challenger Drive, close to U.S. Highway 67 in Red Bird, and dozens of Dallas Fire-Rescue vehicles responded.

Also read: Dallas air show crash: Where is Dallas Executive Airport?

Both aircraft, according to the Commemorative Air Force, departed from Houston.

The number of passengers on board the aircraft was unknown. About two o’clock in the afternoon, Jason Evans, a Dallas Fire-Rescue spokesman, said he was unaware of the condition of the pilots or of any reports of injuries among ground personnel.

Also read: Watch: Dallas air show aircraft crash

Social media users posted videos of the B-17 slamming into a smaller plane as it turned. The B-17’s front was torn off, and when it impacted the ground, its wings burst into flames.

In a tweet, Dallas Mayor Eric Johnson described the accident as a “terrible tragedy in our city” and noted that there were still many unanswered questions regarding it.

“The videos are heartbreaking,” Johnson wrote. “Please, say a prayer for the souls who took to the sky to entertain and educate our families today.

Ted Cruz, a senator from Texas, stated that he and his wife, Heidi, were “praying for those involved.”

“The images of this collision are incredibly distressing and we pray for the safety of everyone on the scene,” Cruz tweeted.

According to the organizer’s website, the event has been postponed from Saturday through Sunday.

Debris from the crash flew onto Highway 67 in the southbound direction. Following the incident, the highway’s southbound and northbound lanes were closed, according to the Dallas Police Department, CNN reported.