AUGUSTA — A guard inside the Edmund S. Muskie Federal Building in Augusta shot a man Wednesday morning who was armed with a knife, according to the FBI.

At about 11:30 a.m., an unidentified man with a knife entered the building at 40 Western Ave., which houses a post office and several federal offices, including the Internal Revenue Service.

The man allegedly assaulted one of the Federal Protective Service guards there. Another guard then shot the man, wounding him.

The suspect was taken into custody and brought to MaineGeneral Medical Center in Augusta with an abdominal wound, according to the FBI’s Boston office and officers at the scene. His condition was not known Wednesday afternoon.

The FBI said no one else inside the building was injured.

The security company employing the armed guards, Paragon Systems Inc., contracts with the Federal Protective Service to scrutinize people who visit the Augusta building. The Federal Protective Service is a branch of the U.S. Department of Homeland Security.

The FBI was leading the investigation into the alleged assault and the shooting, with assistance from Federal Protective Services and the U.S. Attorney’s Office, Maine State Police, Augusta Police Department and Office of theMaine Attorney General’s investigations office.

The FBI’s Evidence Response Team was processing the crime scene.

FBI officials declined to provide additional information, including the identities of the guards involved.

Local, state and federal police officers and Augusta Rescue responded to the Muskie Federal Building. The main entrance to the facility was blocked into the afternoon with police tape.

Police at the scene declined comment and said the incident was under investigation by the FBI.

Multiple police cruisers, including from Augusta police and Federal Protective Service, were at the Sewall Street entrance to the building into the afternoon, and the entrance remained closed, although the rest of the building and its parking lot appeared to remain open.