LONDON — A knife attack that wounded three people in a busy train station in Manchester, England, is being investigated as an act of terrorism, the police said on Tuesday.

Moments after the stabbing Monday evening at Manchester Victoria station, the police arrested a 25-year-old male suspect in the station.

“We are treating this as a terrorist investigation,” Chief Constable Ian Hopkins of the Greater Manchester Police said in a statement. Officers “were working throughout the night to piece together the details of what happened and identify the man who was arrested.”

The authorities did not release the suspect’s name — in fact, it was not clear that they knew his name — or give a motive. Chief Hopkins said that officers searched the man’s home in the Cheetham Hill area of Manchester on Tuesday morning.