British police say they have arrested a 19-year-old man on suspicion of a terrorism offense over a suspicious package discovered on a London subway train.

The Metropolitan Police force says officers used a stun gun while detaining the man Friday on a busy city street. He is being held on suspicion of "the commission, preparation and instigation of terrorism acts."

North Greenwich subway station was closed for several hours Thursday after the discovery of what police called a "suspicious item" on a train.

The object was destroyed in a controlled explosion. Police say they await the results of a forensic examination to discover what it contained.

Police say they are not looking for anyone else as part of the investigation and are keeping an open mind about motive.