There was no gas leak in the incident.
The early morning mishap at Madapally near Vadakara prompted authorities to close the section of the highway and divert traffic as a precautionary measure while efforts were on to transfer the fuel to another vehicle, they said.
The tanker was coming from Mangalapuram to Kochi when its driver attempted to overtake a car and collided with the fish-ladden mini lorry.
Drivers of the two lorries and the car were injured and had been admitted to the Medical College Hospital here, Sub-Inspector of Police Chombala Haris said.
There have been several accidents involving LPG tankers in Kerala in recent years. In August 2012, an LPG tanker exploded after hitting a road divider at Chala in neighbouring Kannur District, killing 20 people and injuring scores.