MONTREAL -- Quebec's acting public security minister says an emailed threat to schools in many parts of the province led to closures, bomb sweeps and a beefed up police presence on Tuesday.

Pierre Moreau said Tuesday some 61 institutions were affected by the threat.

Moreau said the threat in question was a single email that was sent to some primary and secondary schools as well as some junior colleges in various cities across the province. He said it threatened that bombs could be planted over several days up until Friday and that thus police will keep a close watch.

Quebec Provincial Police said they hadn't turned up any explosive devices as of Tuesday afternoon and that 53 schools were given the all-clear.

The missive was authored by a so-called coalition Moreau identified as "Red Sceptre" -- a group unknown to authorities.

Police intelligence caught wind of the threat early Tuesday, with the email being sent to institutions and school boards directly. Moreau said it complained of the quality of education and the attitude of teachers and their union.

Moreau said an email with the same content was sent to each institution, suggesting bombs being set at specific times and implying the complicity of those working in some of the institutions.

He added that there were threats in Ontario also.

North Bay police said there was a threat to Canadore College on Tuesday morning. Sgt. Jim Kilroy said police searched the campus with "negative results."

Ontario's education ministry said the Toronto District School Board also received a bomb threat, but it was not made to any specific school and no schools were locked down or evacuated.

Moreau said the Quebec threats are under investigation by provincial police.

Moreau said the email was not related to the labour negotiations between the province's teachers and the government over a new collective agreement, although the document refers to ongoing pressure tactics by teachers.

A spate of schools and institutions, both French and English, from various parts of the province were closed after the threat, with some electing to shut for the day.

Schools were searched in Western Quebec, in the Abitibi region, and in Sherbrooke as well as certain establishments in Montreal and Quebec City. Evacuation orders also affected junior colleges in several cities, including Trois-Rivieres and Drummondville.

Moreau mused the actions could be considered a terrorist attack, given the impact on a large portion of the population.

Premier Philippe Couillard told reporters at the provincial legislature his immediate thoughts went to many worried parents across the province.

"It's a disgusting act, a cowardly act," Couillard said. "I know that the police inquiry will follow its course and if the inquiry identifies the responsible people, they will be prosecuted to the most severe extent that they can."