GLENSHAW, Pa. — An FBI agent was shot and killed today while serving a warrant at a home near Pittsburgh.

The agent was shot at around 6 a.m. in Indiana Township, about 10 miles northeast of Pittsburgh, said FBI Special Agent William Crowley, a spokesman for the agency in western Pennsylvania.

The agent's name was not immediately released. It's also unclear who shot the agent and whether anyone had been arrested for the shooting. Neither federal nor county officials would confirm reports that a suspect was in custody.

Crowley would not say what the warrant was for. A roundup of drug suspects was happening in the greater Pittsburgh area and federal drug and FBI agents were at the scene, but Crowley wouldn't comment on whether the shooting was related to the roundup.

At the federal courthouse in Pittsburgh, federal public defenders were in a courtroom Wednesday morning waiting the arrival of some 35 people who were arrested in the drug sweep. Indictments in the case were sealed, but they were expected to be unsealed once the defendants appeared in court.

The shooting happened at a cream-colored house that backs up to fields and woods. A child's basketball net and play fort could be seen in the backyard. Authorities remained on the scene Thursday morning, blocking the street to the public. Several police cars, including unmarked cars, lined the street.

Emergency dispatchers had initially said the victim was a police officer shot in a home invasion.

The last FBI special agent killed in the line of duty was Barry Lee Bush, who was accidentally shot and killed by a fellow agent outside a bank on April 5, 2007, in Readington, N.J., according to the FBI. Bush, 52, of Forks Township, Pa., and other agents were in pursuit of three bank robbers who were armed but did not fire their weapons, authorities said.