An unidentified runner from Virginia died today during the Army Ten-Miler race, collapsing about 200 yards from the finish line at the Pentagon.

Arlington County medics took the runner to George Washington University Hospital in Washington, D.C.

The cause of death is not known. Officials say the runner was a civilian, not a member of the military.

The race started in 70-degree heat and high humidity. Race officials say there was plenty of water and first-aid stations along the course.

More than 25,000 people registered for the 23rd annual race — the largest 10-mile race in the United States. The course runs from the Pentagon, across the Potomac River through the streets of Washington, past the Capitol and back to the Pentagon.