Toronto-area residents woke up to an emergency alert on Sunday morning about an unknown “incident” at a nearby Canadian nuclear plant that officials later said was mistakenly sent.

The alert was sent to everyone in the province of Ontario just before 7:30 a.m. local time, warning about “an incident” that took place at Pickering Nuclear Generating Station, according to Buzzfeed News. It said there was “no abnormal release of radioactivity” and that people in the surrounding needn’t take any vigilant measures. The alerts said the emergency only applied to people within a 10-kilometer (6-mile) radius of the power plant, but it was also sent to people living farther away, Bloomberg reports.

A little after 8 a.m., Ontario Power Generation, which runs the facility, tweeted that the alert was sent erroneously and that the public and environment weren’t in jeopardy.

In a statement to Buzzfeed, the power company said that it was working alongside local officials to investigate the situation, restating that “there is no danger to the public.” The statement continued, “There was no radiological event. The alert was issued in error.”

Almost two hours after the original alert, people received a second emergency message that said the previous alert was a mistake and that there was “NO active nuclear situation” at the Toronto facility.

Pickering Mayor Dave Ryan took to Twitter, “demanding that a full investigation take place.”

Toronto Mayor John Tory also called for an investigation.

The alert caused a scare, with many taking to Twitter to make references to the X-Men, the HBO miniseries Chernobyl, and more.

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