A stabbing attack at a festival in Solingen, a city in western Germany left four people dead and four others with severe injuries, CNN reports.

The attack happened at Fronhof, a square in the city center, Euro News reports. The police have begun a search to find the attacker, who remains at large. They haven’t dismissed terrorism as a possibility.

The City Marked Its 650th Birthday

The “Festival of Diversity” happened during the weekend to mark the city’s 650th birthday, CNN said quoting police. Pictures and clips from the event showed many ambulances, cops, and a chopper in the sky.

Solingen, a city with around 160,000 residents, is located near Cologne and Düsseldorf. The local paper, Solinger Tageblatt, reported that authorities told people to leave the downtown area.

Authorities Had Not Made Any Arrests Yet

A report from the German news agency dpa, citing unnamed police sources, said the weapon was likely a knife, and no arrests had been made yet. “Tonight, everyone in Solingen is feeling shock, horror, and deep sadness,” wrote city mayor Tim Kurzbach on Solingen’s Facebook page. “We wanted to celebrate our city’s anniversary together, but now we must mourn the dead and injured.”

The mayor expressed gratitude to the rescue and security teams for their help and sent prayers to the victims who are fighting for their lives. The three-day “Festival of Diversity” began on Friday, featuring music, food, performances, and family-friendly entertainment, according to the festival’s website. More details are expected soon.