9/11 flag lost in Flight 93 memorial fire

• Flag that flew over U.S. Capitol on 9/11 is destroyed in a fire


• Friday's blaze destroyed headquarters of Flight 93 National Memorial in Pennsylvania


• Headquarters complex is about two miles from the memorial


• Flight 93 crashed on September 11, 2001, after hijackers took over the plane

(CNN) -- The flag that flew over the U.S. Capitol on September 11, 2001, was destroyed in a fire at the headquarters of the Shanksville, Pennsylvania, memorial to United Airlines Flight 93, the National Park Service said Saturday.

The blaze Friday destroyed the headquarters complex of Flight 93 National Memorial, dedicated to the 40 passengers and crew who died when Flight 93 crashed outside the town in southwestern Pennsylvania during the deadliest terror attack on U.S. soil. The plane went down, killing all on board, as passengers fought back against the hijackers, according to investigations.

Investigators said the terrorists were most likely trying to turn the airplane toward Washington to hit a major political target, such as the Capitol.

In a statement, the National Park Service said the items that survived the fire included the majority of 820 oral histories conducted since 2005, the archival photo collection and 480 DVDs containing tens of thousands of images of the crash scene, investigation, temporary memorials and construction of the permanent memorial.

"Unfortunately, the flag that flew over the U.S. Capitol on September 11, 2001, was destroyed," the statement said.

The flag was donated by former House Speaker Dennis Hastert during last month's 9/11 anniversary ceremony at the crash site.

Also lost in the fire were a handful of personal items of passengers and crew recovered from the crash site and from families, copies of DVDs of the annual commemoration ceremonies and meetings of the memorial's federal advisory commission, and about 100 "tribute items" to the passengers and crew left by visitors since 2001.

NPS spokesman Mike Litterst said the fire was being jointly investigated by the National Park Service and Pennsylvania State Police. The cause has not been determined.

Litterst told CNN affiliate WJAC that the buildings had fire alarms but no sprinklers.

Some charred documents have blown away from the fire scene and can be found on the grounds, Litterst said.

"We've got museum recovery teams to help us salvage items that may be smoke damaged or fire damages," he said.

A memorial employee, who is also a member of the Shanksville Volunteer Fire Department, suffered minor first-degree burns attempting to extinguish the blaze, which started about 3 p.m. Friday.

"We continue to be grateful that there was no loss of life to visitors or employees, especially given the speed with which the fire engulfed the structures," Litterst said in the statement.

Ken Nacke, whose brother Louis was on Flight 93, helped raise funds for the Flight 93 National Memorial and advised in its planning.

"It's heartbreaking that we spent all this time to have this happen," he said Friday. "All the blood sweat and tears that went into building this."

Neither the memorial itself nor the new visitor center currently under construction -- both located about two miles from the headquarters -- were affected, Litterst said.

The memorial's visitor center will include traditional and interactive exhibits, public programs and information about the history of Flight 93.

United Airlines Flight 93 was traveling from Newark, New Jersey, to San Francisco when hijackers took over the plane, according to the 9/11 Commission.

Since 2001, more than 1 million people from around the world have visited the crash site.

What you need to know about the Flight 93 National Memorial

CNN's Aaron Cooper, Deanna Hackney and Laura Bernardini contributed to this report.