A source at the Integrated Security Service, or ECU-911, said the school vehicle "was not following a route," so it carried no passengers during the Friday evening accident.

The agency did not specify how many passengers were travelling on the inter-provincial service bus. An off-road vehicle was also involved in the crash on the road between the southwestern coastal towns of Yaguachi and Milagro.

Road accidents are one of the leading causes of death in Ecuador.