OTTAWA — A man was in police custody Wednesday after a suspicious package forced the evacuation of the office block that houses the prime minister's office.

The 11:15 a.m. incident sent employees from the prime minister’s office and the privy council office spilling onto the Ottawa streets as police officers and fire crews descended on the scene.

Police blocked off traffic along Wellington St., a main thoroughfare that runs in front of Parliament Hill, and quickly set up a large cordon around the building.

Officers were investigating a suspicious package that apparently had been left inside. An explosives unit from the Ottawa Police Service was called to the scene. Shortly after 2 p.m., officers deemed that the package no longer posed a threat and employees were allowed to return to their offices, RCMP Cpl. Lucy Shorey said.

“An individual was apprehended at the Langevin building shortly after the incident,” Shorey said. “He is currently is still in custody and the investigation is ongoing.”

Harper was not in his Langevin Block office at the time. He was across the street on Parliament Hill.

The building was evacuated as a precaution and a joint RCMP-Ottawa police team that deals with potentially hazardous materials was called to the scene.

Shorey declined to provide details about the person of interest or the package but said police hoped to release additional details Thursday morning.

The incident came as the government was making its final preparations for Wednesday’s speech from the throne, which sets out its parliamentary agenda for the forthcoming parliamentary session.

With files from Curtis Rush