TORONTO (AP) — People throughout the Canadian province of Ontario awoke Sunday to a cellphone alert warning them of an “incident” at a nuclear plant just east of Toronto — only to later be told the message was a mistake.

The message, which was transmitted throughout the nation’s most populous province, was accompanied by a shrill emergency broadcast noise. It said an unspecified event had occurred at the Pickering Nuclear Generating Station. There was no abnormal release of radioactivity, it added, and people did not need to take protective action.

More than an hour later, utility officials sent another message saying the alert “was sent in error” and that there was “no danger to the public or environment.”

“No further action is required,” said the message, which was also sent to television screens.

The alert went out during a routine training exercise being conducted by the Provincial Emergency Operations Centre, Ontario Solicitor General Sylvia Jones said in a statement that apologized for the mistake.

She said the government had started a full investigation and would “take the appropriate steps to ensure this doesn’t happen again.”

Jim Vlahos, a 44-year-old Toronto man, awoke to the alert and quickly made a hotel reservation more than 60 miles away in Niagara Falls. He said he figured he would go as far west as possible and then cross the border.

“Having watched ‘Chernobyl’ didn’t help,” he said, referring to the HBO show about the 1986 nuclear disaster in the Soviet Union. “The lack of communication following the alert didn’t help either,” he said.

“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.”

Many people slept through the first alert and saw it was a false alarm by the time they woke up.