Chennai: Two drivers died, and five bus passengers suffered injuries in an accident involving three vehicles near Ulundurpet on Monday.Police said Marimuthu, 47, of Velachery was driving a mini-bus chassis vehicle from Chennai to Trichy. When it reached Sengurichi near Ulundurpet in the early hours of Monday, the driver, whom police suspect may have dozed off, lost control and crashed into a median on the highway.The impact severely damaged the front portion of the vehicle, and Marimuthu died on the spot. Within no time, a private bus travelling from Devakottai to Chennai collided with the crashed vehicle, and five passengers in the bus sustained minor injuries.The collision pushed the mini-bus chassis vehicle onto a nearby road, where it crashed into a mini lorry carrying goods from Chennai to Trichy. Sudharsan, 21, of Mecheri in Salem district, who was driving the lorry, died on the spot.The pile-up caused severe traffic congestion on the national highway for several hours.