At least nine construction workers were killed and five injured when a partially-constructed bridge collapsed in central Colombia on Monday, an official from the disaster response agency said.

The bridge, located in Chirajara on the border of Cundinamarca and Meta provinces, was to be part of the highway that connects the capital Bogota and the city of Villavicencio, and was not yet in public use.

The cause of the collapse, which sent pieces of the bridge down into a canyon below, is under investigation, Reinaldo Romero, head of disaster response for the Meta province, told Reuters.

Transportation Minister German Cardona flew over the site of the collapse later on Monday and visited rescue staff on the ground with Dimitri Zaninovich, the head of the national infrastructure agency.