WASHINGTON — Someone fired shots at the Pentagon early Tuesday in what security officials described as “a random event.”

No one was injured in the pre-dawn incident in which shots were fired into two windows at the sprawling Defense Department building just across the Potomac River in suburban Virginia.

Steven Calvery, director of the civilian Pentagon Force Protection Agency, told reporters that a number of his officers reported hearing five to seven shots at about 4:55 a.m. near the south parking lot of the Pentagon. The Pentagon building and the roads leading it were briefly shut down as officers conducted a sweep of the area.

An internal search of the iconic structure found fragments of two bullets still embedded in two windows — one on the third floor and one on the fourth. The bullets had shattered but did not penetrate the windows, Calvery said. The windows were part of offices that are being renovated and they were unoccupied at the time.

Calvery said he didn’t know what kind of weapon was used but that it was probably a high-velocity rifle. No suspects were arrested.

“Right now we consider this a random event,” he said.

But Calvery also said authorities were looking at whether the shooting was related to Sunday’s discovery of bullet holes in windows at the National Museum of the Marine Corps in Triangle, Va. The museum is associated with the Quantico Marine Base, about 30 miles south of the Pentagon.

A rifle is also believed to have been used in that shooting, which may have occurred in the early morning.

Pentagon investigators worked with the FBI as well as Arlington, Va. police, who helped sweep the area, and Virginia State Police, who closed part of nearby Interstate 395 to search for evidence.

At about 9 a.m., a dozen officers walked side by side in a line as they combed a grassy area on the south side of the building.

Calvery said investigators were talking to construction workers who also heard the shots. He said it was possible the shooter had stood on the roof of a nearby building.