Four youth — Aboobacker, Akbar, Azlam and Salim — were taken into custody by the sleuths of Tamil Nadu Police’s Q-Branch from Vellore and surrounding areas on Thursday in connection with Wednesday’s bomb blasts in Bangalore. More than 15 persons were injured in the blasts which took place near the BJP office. The probe centred around the 100-cc bike which was used to detonate the improved explosive devise. The police were tight-lipped about the arrest of the four persons.