Counterterrorism police arrested a teenager in London on Friday after a “suspicious item” was found on the subway, officials said.

The 19-year-old suspect, who has not been identified, was shot with a Taser and detained in north London, according to a statement from the city’s Metropolitan Police.

The force said he was arrested on suspicion of “the commission, preparation and instigation of terrorism acts.”

The arrest came around 24 hours after officers were called to North Greenwich subway station, in the southeast of the city, to reports that a suspicious item had been left on a train.