Authorities say a van crashed into a crowd Saturday outside a popular bar in the German city of Muenster, killing three people and injuring 20 others. The driver of the vehicle shot and killed himself after the crash, local police said. Six of the injured are listen in critical condition.

It’s not yet clear who the suspect is or what the motive is. Police said they are examining reports that other suspects may have fled the crash scene.

The incident is being treated as terrorism, but the suspect’s identification has not yet been transferred to the U.S., a U.S. intelligence source told CBS News.

Germany’s Sueddeutsche Zeitung newspaper reports that the suspect’s apartment was being searched for possible explosives.

On Twitter, local police warned residents to “avoid the area near the Kiepenkerl pub” in the city’s historic downtown area where a large-scale police operation was underway.

Police said a suspicious object was found in the van and they’re still examining it to see if it is dangerous. They told German news agency dpa that the object was the reason why a large area around the scene was sealed off after the crash.

Residents said they were enjoying the first warm afternoon in the area that features many shops and cafés, CBS News correspondent Roxana Saberi said on CBSN. People were outside enjoying themselves, many of them college students, enjoying the weather.

Muenster, a major university city, has about 300,000 residents and an attractive city center rebuilt after World War II.

Daniel Kollenberg, a witness, said there was a heavy police presence at the scene, with dozens of police vehicles and several police helicopters. “It’s quite chaotic because it’s pretty calm here,” Kollenberg told BBC News.

A spokeswoman for German Chancellor Angela Merkel said “our thoughts are with the victims and their families” who were killed and injured when a vehicle crashed into a crowd in the western German city of Muenster.

Ulrike Demmer, a spokesperson for the German government, tweeted that the crash was “terrible news.”

Germany has experienced a number of terror attacks in recent years, including through the use of vehicles. In December 2016, a truck plowed into a crowd at Christmas market in Berlin, killing 12 people.