Police said those killed include a pedestrian who was hit by the truck before it rammed into the matatu at Rupingazi area.
According to police, two women, a man and a child died instantly while two other men died while undergoing treatment at the Embu Provincial General Hospital.
Traffic Commandant Benson Kibui told Capital FM news that initial investigation had shown the truck driver was drunk at the time of the accident.
“The driver was drunk, it was totally irresponsible,” he said. “These are the kind of accidents which can be avoided.”
A resident who witnessed the accident said the truck was being pushed when it lost control and hit a station wagon vehicle that was being repaired on a roadside garage before hitting the matatu that was picking passengers.
The witness said the impact of the collision hurled the matatu about 50 metres from the spot where it was picking passengers and only stopped when it hit a tree.
Eastern Provincial Traffic Enforcement officer Martin Asin said the driver had been arrested and would undergo medical tests to ascertain if he was under the influence of alcohol.
Asin said the truck which was transporting animal feeds had been parked at a nearby fuel Station since Wednesday.
Anthony Mugendi, a conductor of the ill-fated matatu escaped unhurt.
“I heard a loud bang which I thought was a bomb that had gone off. I don’t even know of the whereabouts of the driver,” Mugendi said, still in shock.
Another witness Frida Nyawira, said she counted seven bodies being removed from the mangled wreck of the matatu.
“Among the dead was a woman who was on the roadside waiting to board a vehicle,” she said.
“I saw her being knocked down as she had ran in the same direction where the matatu was being pushed. I also saw a boy whose hand had been cut off and was lying on the ground,” Nyawira recounted.
Four other people died on Wednesday in separate road accidents in Nakuru and Kisii.