U.S. prosecutors unsealed indictments against 17 alleged leaders of Colombia's largest cocaine-trafficking organization in a move seeking to shore up bilateral cooperation in the drug war.

The charges against members of the so-called Usuga clan were announced Tuesday by Colombian President Juan Manuel Santos and Miami-based U.S. Attorney Wifredo Ferrer.

Colombian authorities in recent weeks have arrested dozens of members of the Usuga clan. The criminal network is accused of smuggling hundreds of tons of cocaine into the United States by operating clandestine flights to partners in Central America.

The group's top leader, Dairo Antonio Usuga, better known by the alias "Otoniel," has so far eluded capture despite a nationwide manhunt involving more than 1,000 officials. The U.S. has offered a $5 million reward for information leading to his arrest.