Hamburg police said on Saturday that four of the victims who had sustained life-threatening injuries were in a stable condition. Officers arrested a 39-year-old German woman at the scene of the attack, which took place at about 18:00 local time (16:00 GMT) on Friday.

The suspect in the recent knife attack at Hamburg's central train station was released from a psychiatric hospital on the day before the stabbing, officials said on Sunday. The 39-year-old woman had been treated in a psychiatric institution in the northern German city of Cuxhaven for three weeks after she was found in a state of helplessness in early May,

At least 18 people were injured, including four critically, in a stabbing attack at a train station in Germany on Friday, authorities said. The suspect in the stabbing -- a 39-year-old woman -- has been arrested, police said. A magistrate has ordered the suspect to be placed in a psychiatric institution, Hamburg police told ABC News on Saturday.

Seventeen people were injured in a knife attack at the central train station in the northern German city of Hamburg on Friday, with four of them suffering life-threatening injuries in the incident, emergency services said.

A woman allegedly stabbed 17 people in a knife attack at Central Station in Hamburg, Germany, on Friday, May 23. The woman had given herself up to the police without resistance, and an investigation into the incident is ongoing.

Police said the suspected assailant was a 39-year old woman who allowed herself to be arrested without resistance.