RCMP investigators say the bomb threat against P.E.I public schools was "not credible," after conducting physical checks of every school on the island Wednesday. Schools across the island have been given the go-ahead to resume classes Thursday.

The threat to island schools was initially delivered to RCMP in Ottawa via fax on Wednesday morning. The threatening message said that bombs were placed in several P.E.I. schools and would be detonated the same day, but did not specify which ones.

Some schools in Nova Scotia and Manitoba were also threatened Wednesday, but police are still investigating whether the threats are linked.

He said the schools were notified within 10 minutes and evacuations began as quickly as possible. All students are safe and there were no injuries during the evacuations, Baillie said.

Students were led by staff to designated safe areas in the communities. Some have boarded busses heading home. Parents who normally pick up children for early dismissal may do so at the designated safe areas, where staff will be providing supervision until all children are picked up, authorities said.

The P.E.I. public school board, which comprises 62 English and French schools, has approximately 19,000 students.

P.E.I. RCMP Sgt. Kevin Baillie previously told reporters that officers attended each school on the island, but could not confirm that every school was actually searched for explosives. He said bomb disposal units or sniffer dogs were not dispatched.

Baillie said that school staff should search the buildings for anything suspicious and let the authorities know.

The RCMP later clarified that police will "investigate any unusual items in Island schools."

"Teachers are encouraged to inform RCMP of any unusual or out of place items in the schools for investigative follow-up by RCMP members," the Mounties said in a statement.

"We don’t know who is responsible for these threats," Baillie said, but there is an active investigation.

Parker Grimmer, director of the P.E.I. Public Schools Branch, said he was "impressed" by how quickly school staff reacted to the threat and followed evacuation protocols, but added that there will be "an opportunity to debrief" and discuss whether communication in emergency situations can be improved in the future.

Prime Minister Justin Trudeau said he has been assured that all P.E.I. students are safe and that "the situation is under control."

"As a parent, I know how worrisome this type of situation can be," he told reporters in Ottawa Wednesday afternoon. "I know that the affected parents must be having a very difficult day."

Trudeau said the federal government will continue to monitor the situation and is confident that local authorities are "deploying all necessary resources to this ongoing operation."

The University of Prince Edward Island also tweeted Wednesday morning that it is closing for the day.

A university spokesperson told CTV News that the campus did not receive a direct threat, but was exercising caution.

Three schools in Nova Scotia -- Cape Breton University (CBU) and the two campuses of the Nova Scotia Community College (NSCC) – were also evacuated on Wednesday.

The initial police investigation at NSCC has concluded and the CBU campus has been given the all clear to re-open. Classes and administrative offices will remain closed for the day and resume as scheduled tomorrow morning, according to the university.

Both NSCC campuses received bomb threats just before 8 a.m. local time, police said.

Schools in Winnipeg were also threatened on Wednesday, and police believe the two incidents are connected.

Police say education officials received a fax this morning threatening Winnipeg's largest school division.

However, unlike their counterparts in Atlantic Canada, schools weren't shut down. It was thought to be a hoax, although students were given letters detailing the threat.

Some parents said they were concerned about how it was handled.

"It makes me worried because I have all my kids in this school here, and I want to be able to drop my kids off and feel safe when they're here."

However, both police and school officials say they followed standard procedure.

School officials immediately notified police of the threat, an investigation was started, staff were briefed and the schools were not put into lockdown.

"It didn't seem to make sense (to shut schools) if we didn't think the threat was justified and was serious," said Const. Rob Carver, with the Winnipeg Police Service. "And we didn't."

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With files from The Canadian Press