Nakashipara/Raiganj: A sub-inspector, a constable of North Dinajpur district police and a driver were killed and another constable was seriously injured when the Bolero they were travelling in rammed into a stationary truck from behind on NH34 in Nadia's Nakashipara early on Monday morning.

Police said the driver of the Bolero had apparently dozed off.

The driver, who was hired by the police, along with the two policemen, died on the spot. The accident occurred at Gacha village near Bethuadahari town, about 145km from Calcutta, around 5am.

"They were going to Bhawani Bhavan in Calcutta with service-books of police personnel in North Dinajpur district. It is an unfortunate incident. We are in touch with the Nadia district police and sent a team on Monday morning to the spot," said Anoop Jaiswal, the superintendent of police of North Dinajpur.

Sources said the policemen had hired the SUV and started for Calcutta on Sunday night. The deceased were Mohammad Masood, 51, a sub-inspector posted as reserve officer in the district police, Tarun Das, 47, a constable and Prabhash Das, 28, the driver.

The injured constable, Satyabrata Basak, has been admitted to Saktinagar district hospital in Krishnagar. They were residents of Karnajora and Debinagar in Raiganj.

Farmers going to market early in the morning, who witnessed the incident claimed that the Bolero had zigzagged on the highway for about 200m before the crash.

A patrolling vehicle of Nakashipara police station reached the spot and took all the occupants of the mangled SUV to Bethuadahari block hospital where three of them were declared dead on arrival.

An officer of Nakashipara police station said: "After preliminary investigation, it appears the driver of the vehicle had most probably dozed off. However, we are waiting to know what exactly happened from the injured constable who is now unconscious."

Doctors at Saktinagar district hospital said the condition of the injured constable was critical.