CNN  — 

Several people have sustained “life-threatening injuries” in a knife attack at Hamburg’s Central Station, German police said Friday evening.

Police said they have arrested a 39-year-old woman, who they believe acted alone, after a major police operation.

There are currently no reliable figures on the number of injured people, they added.

Investigations into the incident are ongoing.

Hamburg’s Central Station is the busiest passenger railway station in Germany, with more than 550,000 travelers per day, according to the city’s website.

This is a developing story and will be updated.