BERLIN (AP) — Local authorities say an alert about a possible attack at a school in western Germany that prompted a major police operation Wednesday was a false alarm.

Armed officers rushed to the Hoenne vocational school in Menden after receiving an alert before noon.

“The report of an attack in Menden was a false alarm,” the authorities for the Arnsberg district said in a message on Twitter. “Thanks to all of the emergency responders who reacted so quickly.”

A spokesman for Menden police earlier told German broadcaster n-tv that officers had found no evidence of an attacker or any injured persons

The spokesman, Marcel Dilling, said a portable alarm had been triggered from inside the school.

Eiko Pate, a journalist at local broadcaster Radio Hellweg, said students at the school had been told to lock themselves inside their classrooms.

Local media later reported students were evacuated from the school by police.

Germany has seen a number of shootings at schools over the years. In March 2009, a 17-year-old student killed 15 people and then himself in the town of Winnenden.