U.S. Capitol Police officials are reviewing reports that tactical team members were ordered to leave the scene after they responded to Monday's shooting at the Washington Navy Yard.

A Capitol Police officer said he thinks officers could have made a quick entry into the building where a gunman opened fire, killing 12 people. "We were definitely the closest tactical team in the city," he said. "It was at the scene very early on, within a couple of minutes. They were ordered to disengage and turn back — for what reason, we don't know."

A Capitol Police spokesman said the department "offered and provided mutual support and assistance" at the Navy Yard.

The allegation — first reported by the BBC and a Washington-area TV station, WUSA-9 — does not specify where the team was located and at what point during the incident it arrived. It was not clear whether the Capitol Police would have entered the building along with other responders or whether D.C. police had asked them to respond.

The labor union for the Naval District Washington Police said seven officers were on duty at the base Monday morning, down from 12 before budget cuts three years ago, and only the chief was on roving patrol duty.