Envelopes containing white powder labelled "Ottawa shooting" were delivered to senators' offices in Ottawa Monday, but authorities have determined the substance was not toxic.

The Senate Protective Service sent out a note just after noon alerting Parliamentarians and saying two senators' office have received these envelopes.

A spokeswoman for the Senate said the latest internal reports say several more envelopes have been found as well but it's not clear whether these were sent to MPs or senators.

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Hours later, Patrick McDonnell, Deputy Sergeant-at-Arms and director-general, protective service, for the House of Commons, advised that the packages were not noxious.

"Further to the message sent earlier today regarding envelopes containing white powder, law enforcement authorities have confirmed that the substance is non-toxic," Mr. McDonnell said in an e-mail. "Additional mail scanning protocols continue to be in place and we ask that you continue to exercise vigilance when handling incoming mail."

Newfoundland Senator David Wells said via Twitter that his office received one of the envelopes.

Earlier this month, four letters containing white powder were sent to the Quebec riding offices of four federal cabinet ministers. Provincial police later confirmed the packages were harmless.