A suspicious envelope that prompted a police investigation at Brock University and the isolation of 16 people appears to have been a hoax.

The package was opened at 10:30 a.m. Wednesday on the 12th floor of the school's Arthur Schmon Tower, located in the Thistle Complex at the centre of the university campus in St. Catharines, Ont.

Emergency crews were called to Brock University after a suspicious package was opened.
(CBC)

Niagara Regional Police said tests show that a white powder in the envelope was not harmful, but didn't specify what it was.

Police told reporters the envelope also contained a note that made veiled threats.

Six university employees who were exposed to the envelope and seven others working in the mailroom were isolated, police said.

Then an employee spotted a small pile of white powder on the floor of a building in the Walker Complex, to the west of where the package was found. That prompted crews to put three more people into isolation.

Tests later determined the substance found on the floor to be whey powder.

Police said all isolations were done as a precautionary measure.

With files from the Canadian Press