An accidental emergency alert was sent out to millions of Canadians Sunday morning warning of an "incident" at the Pickering Nuclear Generating Station, leaving residents across Ontario in distress.

Within 30-minutes of the alert being sent out, nuclear plant officials tweeted that the message was sent in error. A spokesperson for Ontario Solicitor General Syl Jones says the alert was issued by staff at the provincial emergency operations centre during a training exercise.

"There was no radiological event," a statement from the power company to Buzzfeed News said. "The alert was issued in error."

Pickering Mayor Dave Ryan was particularly distressed by the notice and demanded on Twitter that a full investigation take place.

"Like many of you, I was very troubled to have received that emergency alert this morning. While I am relieved that there was no actual emergency, I am upset that an error such as this occurred. I have spoken to the Province, and am demanding that a full investigation take place."

"I join Pickering @MayorDaveRyan in calling for a full investigation into why this error occurred because there are far too many unanswered questions," added Toronto Mayor John Tory.

For more information, we'll have to wait until an investigation takes place.