Two people died after their vehicle plunged into the Nithi River on the Meru-Embu road Thursday night.
The wreckage of the vehicle was discovered Friday morning by other motorists.
The driver is said to have lost control of the vehicle before it hit the bridge rails and plunged into the river.
The driver and another occupant are said to have died on the spot.
Tharaka-Nithi County Traffic Commandant Mnanzi Chalo said the two, a man and a woman, were previously spotted in Chuka.
Mr Chalo said most road crashes at the bridge occur on weekends.
The bodies were taken to the Chuka General Hospital mortuary.
Maara police boss John Njihia asked the drivers using the Meru–Embu-Nairobi road to drive carefully when approaching the Nithi Bridge.