A major fire destroyed three buildings on Friday at the Flight 93 National Memorial’s headquarters complex in Pennsylvania, near the site of the Sept. 11, 2001, crash of a hijacked airliner.

No one was reported injured.

The 2,200-acre memorial park near Shanksville, about 80 miles southeast of Pittsburgh, features a wall of names that partially surrounds a field where the flight went down, killing all 44 people on board, including four hijackers.

There was no damage to the memorial site itself, in a field where a United Airlines flight went down in one of four suicide hijackings committed by al Qaeda militants on that day.

The three-building headquarters complex is 2 miles away from the crash site.

The cause of the fire was under investigation, the service said in a statement.

The three buildings destroyed in the blaze housed at least 10 percent of the memorial’s collection of artifacts. Many of the artifacts were in boxes designed to be fire proof, Park Service spokesman Mike Litterst said.

Agency staff were unable to gain immediate access to the scene after the fire to determine exactly what contents were damaged. In all, the Flight 93 National Memorial’s headquarters complex was “a complete loss,” according to the park service.

Litterst said employees managed to save a photo collection and an oral history collection from the flames. However, the American flag that flew over the U.S. Capitol on Sept. 11 was destroyed in the fire.

Seven fire companies responded to the alarm, a Somerset County dispatcher said.

The memorial is expected to reopen to the public on Saturday, the Park Service said.

The buildings comprised the park’s headquarters, with conference facilities, storage space and the superintendent’s office. The under-construction memorial and visitors center are about 2 miles away and were unaffected by the fire.

A memorial plaza was completed in time for the 10th anniversary of the attacks in 2011. There are plans for a 93-foot-tall tower with 40 wind chimes.

A visitors’ center is under construction and slated to open in late 2015.