TORONTO -- An emergency alert warning of an unspecified "incident" at a Toronto-area nuclear power plant Sunday morning was mistakenly sent to people across Ontario during a training exercise, prompting an apology from the province's solicitor general.

Phones in Ontario received emergency notifications alerting them to the supposed incident at the Pickering Nuclear Generating Station in Pickering, Ont. shortly before 7:30 a.m. Sunday.

Although the message was sent out to the entire province, as is customary with the Alert Ready system, it stated that the bulletin only applied to people living within 10 kilometres of the nuclear plant.

"An incident was reported at the Pickering Nuclear Generating Station. There has been NO abnormal release of radioactivity from the station and emergency staff are responding to the situation," the notification read.

"People near the Pickering Nuclear Generating Station DO NOT need to take any protective actions at this time."

Ontario Power Generation, which runs the power plant, said on Twitter at 8:06 a.m. that the alert had been "sent in error" and there was no active emergency. This message was echoed in a follow-up emergency alert pushed to phones more than an hour later.

"There is NO active nuclear situation taking place at the Pickering Nuclear Generating Station. The previous alert was issued in error. There is no danger to the public or environment. No further action is required," the follow-up message read.

Ontario Solicitor General Sylvia Jones said late Sunday morning that Ontario Power Generation had nothing to do with the alert being triggered. What really happened, she said, was that a "routine training exercise" being conducted by the Provincial Emergency Operations Centre somehow went awry, unintentionally resulting in the alert being sent to phones.

"The Government of Ontario sincerely apologizes for raising public concern and has begun a full investigation to determine how this error happened and will take the appropriate steps to ensure this doesn't happen again," Jones said in a statement.

She has asked the chief of Emergency Management Ontario, Doug Brown, to launch a full investigation into how the mistake was made, and said she expects the results to be made public.

Toronto mayor John Tory said that the situation was “very disturbing,” and that he’s “glad that there’s a full investigation taking place.”

Jones explained the delay between the tweet clearing up the mistake and the alert containing a correction an hour later as the province needing to be sure that there was no impending disaster.

However, some Ontario residents took that time to start planning for evacuation. Torontonian Jim Vlahos told The Canadian Press that he made a hotel reservation in Niagara Falls after being awoken by the first alert, fully prepared to take his family as far west as he could and then cross the border.

"I have no problem leaving my phone on for these types of alerts," Vlahos said. "But I would expect some more info from the government so I wouldn't have to overreact the way I did."

Jones said there was never any environmental or safety concern related to the nuclear plant on Sunday. In the past, however, there have been a number of potentially dangerous incidents there. Approximately 73,000 litres of demineralized water leaked from the station in 2011, causing no known impacts to human health. There were also no known adverse effects from a leak of radioactive heavy water at the plant in 2014.

Ted Gruetzner, a former vice-president of corporate relations and communications at Ontario Power Generation, said that those living near the Pickering plant should know that emergency tests are conducted regularly, although they do not normally make it to the public's attention.

When an emergency does occur, he said, there are measures beyond phone alerts that come into play, including sirens and other forms of notification.

"People should … have faith in the technology," he told CTV News Channel.

"The people in Pickering … run a very safe plant."

Gruetzner said he was surprised that the message that was sent out didn't include any clear indication that it was part of a training exercise.

"Normally when you're doing drills like this, you put a very clear distinction on the notice that 'this is a drill' – because you sort of assume that they may get out and fall into the hands of people that aren't supposed to see them and you don't want to cause them panic."

False alarms being sent to the public via push alerts have happened before. In 2018, Hawaii was sent into a brief panic after an emergency alert erroneously warned of a ballistic missile heading towards the island. It took just under 40 minutes for officials to issue a clarification that there was no threat.

The Pickering nuclear station generates approximately 14 per cent of Ontario's total electricity. It is expected to be taken out of service in 2024.

With files from The Canadian Press