03/23/2015 03:15 EDT | Updated 05/23/2015 05:59 EDT

White powder sent to 2 senators' offices found to be harmless

White powder in envelopes sent to two senators' offices has been found to be harmless, House of Commons security says, but RCMP are investigating.

A memo from the director of Senate security says two senators' offices had received envelopes containing an unknown white powder. The memo said no employees were showing signs of illness from being in contact with the envelopes.

"Law enforcement authorities have confirmed that the substance is non-toxic. Additional mail scanning protocols continue to be in place and we ask that you continue to exercise vigilance when handling incoming mail," the memo says.

The Senate memo, as well as one from House of Commons security, warned MPs and senators to be on the alert for suspicious packages and to be wary of mail from unknown sources.

The envelopes received by the senators' offices had a return address of "Ottawa shooting," the memo says.

"Unless your mail is from a confirmed source — we ask that you do not open it," Mike McDonald, director of the Senate protective service, states in the memo.