The Delhi Police detained more than 1,500 people for up to two hours and seized about 270 vehicles from its central district during an intensified night patrol to contain street crimes in the national capital, officials said on Tuesday. The intensive campaign between 10 pm and 2 am Monday night came two days after a delivery agent and his associate were allegedly robbed of Rs 2 lakh at gunpoint by four motorcycle-borne men inside the busy Pragati Maidan tunnel. Seven people have so far been arrested in connection with the Saturday incident.