Multiple people have been injured, including several with life-threatening injuries, in a stabbing attack at a train station in Germany on Friday, police said.

The suspect in the stabbing -- a 39-year-old woman -- has been arrested, police said.

The incident occurred at a train station in Hamburg. A knife was used in the attack, police said.

It is unclear how many people have been injured, Hamburg police said, adding, "However, several people are said to have sustained life-threatening injuries."

Police have not publicly identified the suspect. She is believed to have acted alone, according to Hamburg police, who said they are investigating her background.

This is a developing story. Please check back for updates.