Police in Quebec are investigating after envelopes containing white powder were sent to the district offices of at least two Canadian federal ministers.

It wasn't immediately clear what the powder was.

Infrastructure Minister Denis Lebel's office in the city of Roberval was evacuated Thursday morning after an employee found white powder in an envelope. Two employees who came into contact with the powder remain quarantined in the office as firefighters analyze the scene.

Another envelope containing white powder was found in International Development Minister Christian Paradis' office in the town of Thetford Mines. A police spokeswoman says the person who came into contact with the substance was taken to the hospital.

Police also say a third suspicious envelope has been found in the district office of another cabinet minister.