A vehicle has rammed into an outdoor dining area of a cafe in the western German city of Muenster. Three people, including the suspect, were killed in the incident, according to authorities.

The number of dead was confirmed by the regional interior minister, Herbert Reul, during a press conference. Around 20 people are estimated to have been injured, though the final figure is yet to be announced. At least six among the injured are in critical condition, German media report, citing police sources.

Police have cordoned off the area and asked people to avoid it. The nature of the incident remains “unclear,” police said in a Twitter post urging everyone to “avoid speculation.” According to some media reports, police were looking for explosives in the suspect’s car that was driven into the crowd.

Multiple police cars, ambulances and fire brigades rushed to the scene shortly after the incident. Authorities also scrambled medevac helicopters to airlift the injured to hospitals. Members of Germany’s elite counter-terrorist unit GSG 9 also arrived in Muenster, according to Bild.

Photos from the scene showed a grey minivan, seen among scattered chairs and tables in a narrow street. The café in question, called the Kiepenkerl, is popular among locals and tourists. It is located in the historical part of the city. The street where the incident took place is also located in the vicinity of several major shopping centers.

The driver of the vehicle has taken his own life, German police confirmed to the country’s DPA news agency. Meanwhile, federal police introduced stricter border patrols so that the suspect’s possible affiliates could not flee the country, Spiegel reported.

The incident might have been a terrorist attack, the German Rheinische Post said, citing police sources. However, no official confirmation has been issued.

Investigators said it is unlikely that Islamists were behind the incident, Die Welt reported. “At the moment, the investigation has established that the suspect is a German citizen and not a refugee or the like, as previously thought,” said Regional Interior Minister Reul.

The German Suddeutsche Zeitung daily, citing its own sources, saidthat the man who allegedly plowed the car into an outdoor dining area in Muenster was a 48-year-old German who had mental-health issues, and that there was no evidence suggesting that the incident was a terrorist attack.

Police have searched the man’s apartment for explosives, finding multiple firecrackers and an AK-47 that was broken down, Bild reported.