WASHINGTON (CNN) -- Japanese Defense Minister Gen. Fukushiro Nukaga injured his ankle Monday after a security barricade popped up while his limousine was entering Pentagon grounds.

Five others in the car -- three Americans and two Japanese -- were also slightly injured and taken to a nearby hospital after the 10:15 a.m. EDT accident. They were all treated and released, officials said.

U.S. Defense Secretary William Cohen, who had been awaiting Nukaga's arrival at the Pentagon's river entrance, accompanied the defense minister to the hospital.

An hour after the accident, the black Cadillac stretch limousine still could be seen stuck atop the raised metal barrier, blocking one of several approaches to the river entrance.

John Jester, chief of the Defense Protective Service, said the security barrier unexpectedly popped up after the first few cars in Nukaga's motorcade made it through the gate, lifting the front end of Nukaga's limousine off the ground and bending the car's frame.

Jester says there will be a full investigation into how the accident happened.

Nukaga returned to the Pentagon six hours after the accident to meet with Cohen as planned. "I just bruised my ankle," he told reporters.

"His arrival was more dramatic than I expected, or wanted," Cohen quipped. "Minister Nukaga's determination to be here shows that no barrier can get in the way of the strong security relationship between the United States and Japan."

Cohen said that President Clinton phoned the defense minister from New York to express his concern.

Cohen and Nukaga were slated to discuss a range of security issues, including the development of ballistic missile defenses, said Pentagon spokesman Kenneth Bacon.

CNN Correspondent Jamie McIntyre and The Associated Press contributed to this report.