Four persons- all migrant workers- travelling in the vehicle were rescued from the water by the fishermen.
The jeep carrying the workers was going to Alappuzha from Kochi.
A search and rescue operation involving coastal police, fire department officials and fishermen, has been launched, police said.
The rescued persons have been admitted to various private hospitals at Aroor and Kochi, police said.
Eye witnesses said the accident occurred as the speeding vehicle went out of control the driver, rammed the Aroor bridge's railing and crashed into the lake.