Children were barricaded inside a German school after what appeared to be a false alarm sparked a major police operation Friday morning, according to local authorities and a new report.

Authorities responded to the Max Taut Upper School Center in Rummelsberg, Berlin, after an alarm was triggered there around 10 a.m. local time, police in the German capital city tweeted.

Local reports indicate that talking was banned, “everyone is scared and some students are crying,” according to Metro UK.

“The police take such alarm signals very seriously and have therefore sent the forces to check the situation and search the school,” a police representative told German media.

A photo believed to be from the scene shows around 10 armed police getting out of a van, according to Metro. Twenty-five firefighters were also on scene.

As the investigation went on, police assured barricaded students in a tweet that authorities are “making good progress,” but advised them not to post photos of the rooms on social media “to be on the safe side.”

About five-and-a-half hours after the police operation began, authorities tweeted that they are assuming it was a false alarm and that classes were being led out of the building.

“We always take an amok alarm seriously,” police said in a separate tweet. “The school and our emergency services must always proceed as in an emergency. We ask for your understanding & thank you for your patience. How it came to the false alarm is now being determined.”