The Prime Minister's Office was evacuated on Wednesday after a police explosives team was called in to deal with a "suspicious package" inside – a case that has now reportedly been referred to the RCMP unit that handles national security issues.

Alarms rang out as the Langevin Block building, which is home to the PMO and sits across the street from Parliament, was evacuated shortly before noon local time on Wednesday. Wellington Street, the main drag in front of Parliament, was also closed down.

RCMP said the call came between 11:15 a.m. and 11:20 a.m. An Ottawa Police explosives unit arrived on scene soon after. One "person of interest" is in police custody, Ottawa police said, but no details on charges or the person's identity were released.

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Ottawa police said at 2 p.m. its explosives team was "rendering the suspicious package safe with [a] robot." RCMP later said the "suspicious package [is] not a threat."

CTV reported that the suspect made a bomb threat. Cpl. Lucy Shorey, a spokesperson for the RCMP in the Ottawa region, declined to comment on what, if anything, the individual said. She said the case was referred to the RCMP's O-Division unit, which handles national security threats. "They're still on scene, the matter has been referred to O-Division," she said.

It's unclear, though, if that's the case. Sgt. Richard Rollings, a spokesperson for O-Division, said he could not confirm whether the unit was involved in the investigation, and referred calls back to Cpl. Shorey, who then declined to say whether O-Division was indeed involved.

Meanwhile, Mounties at the scene gave little information.

"We have a suspicious package inside," an RCMP officer said at the scene, declining to give her name. "... I'm just saying there's a situation inside, and that's it."

Prime Minister Stephen Harper gave a speech to his caucus Wednesday morning, and was not inside the Langevin Block building at the time, according to both his office and the RCMP. The PMO referred further questions to the Mounties.

The Ottawa Police Chemical, Biological, Radiological, Nuclear and Explosives team was among several agencies to respond.

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By 3 p.m. local time, the roads around Langevin Block were reopened and staff were seen going back into the building. A police explosives team remained on scene, but Ottawa Police said the situation was now safe. Ottawa Police also said RCMP would lead the investigation.

O-Division is based in London, Ont., and focuses on "organized crime, economic integrity, border enforcement and national security," according to the RCMP website.

The disruption happened as Parliament resumed Wednesday. The Governor-General is set to deliver a Speech from the Throne Wednesday afternoon, outlining the priorities of Mr. Harper's government for the second half of its mandate.