The workers were at the operation to repair a coal silo and were on a high platform when it collapsed.

As of Cerrejon’s most recent update on Sunday, seven of those injured had been released from hospital while five patients continue to receive medical treatment and remain in stable condition.

The workers were employed by contracting companies Conconcreto and Ticom. The deceased were identified as Luis Alfredo Restrepo, Carlos Enrique Perez, Luis Manuel Ricardo and Jairo del Cristo Garcia.

“This is a time of great shock and sorrow for Cerrejon, since the safety of our direct and contracted workers is a core value for us, a value we have applied in practice in the implementation of the highest standards in industrial safety,” the company said.

“Consequently, we have begun a rigorous investigation of this accident. We extend our heartfelt condolences to the families of the deceased workers.”

Cerrejon is owned by BHP Billiton, Anglo American and Xstrata.

The fatal accident is the second for Colombian coal in as many months; in mid-June an explosion and cave in at the small San Fernando underground operation in the northwestern Antioquia province killed more than 70 workers.