LONDON (AP) — U.K. counter-terrorism police have arrested a man in his 20s after a package containing a small improvised explosive device was sent to a residential address in north London.

The Metropolitan Police said the suspect was detained in Cambridge on Saturday morning on suspicion of attempting to cause an explosion, or making or keeping explosives with intent to endanger life or property.

It said armed officers from Cambridgeshire Constabulary’s Armed Response Unit were deployed during the arrest “as a precautionary measure."

The Met said the man had been taken into custody at a south London police station and that officers were searching two addresses in Cambridge.

In a statement, the Met said specialist officers attended reports of a suspicious package in Cricklewood in north London and "made safe what was assessed to be a small improvised explosive device.”