The main gas supply line to Narsingdi was damaged during construction work on a drain, according to Titas Gas authorities
The accident, which took place around 12pm Thursday on the outskirts of the district town, has left another hospitalised, said Gopalganj police OC Md Selim Reza.
He said those who died have been identified as Assistant Sub Inspector Delwar Hossain of the district police, auto rickshaw driver Azad Sheikh, Mujahid Molla, Kulsum and Sumaiya.
He said car collided with the auto-rickshaw on the Dhaka-Khulna Highway at the district's Chechniakandi area.
Three including the police officer and the autorickshaw driver died on the spot.
Four others died while being treated at the state-run hospital in the district town, said OC Reza.