Update, 11 p.m. ET: Despite the fire, the park and memorial will maintain Saturday hours.

A massive fire has left three administrative buildings at the Flight 93 National Memorial in Shanksville, Pa., badly damaged, the AP reports citing the National Park Service.

The AP adds:

"All employees evacuated safely, and no injuries were reported, spokesman Mike Litterst said. He did not immediately know the cause of the fire but said in a statement that initial reports indicated 'extensive damage' to the complex.

"The affected buildings serve as the park's headquarters and include the superintendent's office, Litterst said. The flames didn't affect the memorial or construction of the visitors center, which are about 2 miles away on the large property."

The memorial marks the spot where United Flight 93 crashed during the terrorist attacks of September 11, 2001.

CNN reports that some artifacts — like notes left on a fence near the site — may have been affected by the fire.

"The memorial park is dedicated to the 40 passengers and crew who died when Flight 93 crashed outside the town in southwestern Pennsylvania. The plane went down, killing all on board, as passengers fought back against the hijackers, according to investigations," CNN reports. "The memorial, still incomplete, includes a visitor center with traditional and interactive exhibits, public programs and information about the history of Flight 93."

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