At least 40 people have been killed and more than 30 others injured in Kenya when a tanker carrying flammable substances exploded on the highway after it collided with another vehicle, Kenyan authorities said on Sunday.

The incident occurred on Saturday afternoon about 80 kilometers (49 miles) from Nairobi, on the highway linking the capital with the city of Naivasha.

The truck driver lost control and rammed into a vehicle, causing a multiple vehicle collision.

The injured have either been transferred to local hospitals or to Nairobi for specialized treatment.

A preliminary police investigation indicated that the driver lost control due to a bump on the road.

The highway where the explosion took place is one of the busiest in the country and connects Nairobi with western Kenya and neighboring countries such as Uganda, Rwanda, the Democratic Republic of Congo and South Sudan.