At least 12 people injured in Hamburg train station stabbing

At least 12 people were injured, including three 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.

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. Police believe she may have been in "mental distress."