Railway companies temporarily stopped trains and social media users were in a state of panic after the Meteorological Agency sent a false alarm of a magnitude-9 earthquake across wide parts of the Kanto region Monday afternoon.

The agency issued an erroneous emergency earthquake alert to railway companies and app operators around 5 p.m. The notification warned of a quake measuring 7 on the Japanese seismic intensity scale, the most powerful rank.

The quake would have been as powerful as the one that hit the Tohoku region on March 11, 2011.

“The quake that had been predicted has not taken place,” a Meteorological Agency official said. “It’s an error on our part. We sincerely apologize.”

An official at railway operator Keikyu Corp. said that all of its main line trains stopped in response to the alert, in accordance with the firm’s rules.

All rail services resumed, but trains were as much as 10 minutes late as of 6:30 p.m., the official said.

Yurekuru, a private quake alarm service provider, sent a tweet warning of a quake measuring 7 in Tokyo Bay.

Hundreds of Twitter users retweeted it, with a map showing that vast areas of Kanto were affected.

Rumors circulated on social media about the possible causes, which included a lightning bolt, Godzilla and “Pokemon Go” congestion.