Protective services for the House of Commons and Senate issued separate warnings after the envelopes containing white powder arrived at the offices of two senators.
A later update confirmed that the substance in the envelopes, which carried a return address that read "Ottawa Shooting," was non-toxic.
The office of government leader in the Senate also confirmed that one of the envelope was delivered to Claude Carignan's office.
"We are relieved by the news from RCMP that the contents of the envelope were negative," Carignan's office said in a statement.
"We thank Senate protective services and law enforcement for their prompt response."
Shortly after staff reported something unusual about the envelopes, the RCMP were notified and began an investigation. There were no evacuations from the buildings involved.
Officials said no one who came in contact with the envelopes showed signs of ill effects.
Security officials advised nonetheless that no mail be opened unless the sender can be verified.
"Unless your mail is from a confirmed source – we ask that you do not open it," said an email message from Senate protective services.
Normal procedures dictate that anyone receiving a suspicious package on Parliament Hill avoid touching, opening or moving it.
Staff are also told to isolate suspicious items, to avoid using radios or cell phones near the package and to call an emergency number.
Packages and envelopes can be considered suspicious for a number of reasons, such as if they arrive unexpectedly, they are misaddressed or sent to a generic title instead of an individual, or carry strange markings or return addresses.