La Paz  - At least 21 people died and 55 were injured when a truck on whose trailer they were travelling crashed on a dirt road in the Bolivian province of La Paz, traffic police said Tuesday.

The accident happened on Sunday morning when the truck - which was travelling to the city of La Paz - fell down a 200-metre ravine.

"We first heard about it late Monday, when the injured started to arrive to medical centres in La Paz and El Alto," police said.

The cause of the accident was not immediately known.

Bolivian peasants often resort to trucks as the cheapest means to transport their produce to urban markets. (dpa)