The Canadian province of Ontario sent out an emergency alert reporting an “incident” at a nuclear plant “in error” on Sunday morning, sparking widespread confusion.

Several Ontario residents posted screenshots showing the “emergency alert” they received on their phones around 7:30 a.m. ET. The warning detailed “an incident” being reported at the Pickering Nuclear Generating Station, located in Pickering, Ontario, and said the alert applied to “people within 10 kilometers” of the facility. The warning stated that “there has been NO abnormal release of radioactivity from the station and emergency staff are responding to the situation.” It added the people near the plant “DO NOT need to take any protective actions at this time.”

Ontario Power Generation tweeted about an hour later that the alert was “sent in error” and there was “no danger to the public or environment.”

Pickering Mayor Dave Ryan said he was “very troubled” and “upset” upon receiving the emergency alert and demanded a “full investigation take place.”

Ryan’s request for a full investigation was supported by Toronto Mayor John Tory who noted that many of Toronto’s residents, “especially those who live near Pickering – were unnecessarily alarmed by this alert.”

The Pickering Nuclear Generating Station opened in 1971 and was supposed to be decommissioned this year but Ontario’s government pledged to keep the site functioning until 2024, the Associated Press reported.

This is not the first time things have gone awry at the plant. In 2011, a pump seal failure led to more than 19,200 gallons of demineralized water being spilled into Lake Ontario, according to the AP, which noted that local authorities had said there were no significant negative risks to public health. In 1994, the plant automatically shut down after a faulty valve caused the spillage of 132 tons of heavy water, according to the AP.

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Write to Sanya Mansoor at sanya.mansoor@time.com.