Colombia said Wednesday it was making progress on the transfer of 70 hippos to overseas sanctuaries, but mitigating the havoc caused by this unusual legacy of deceased druglord Pablo Escobar carries a hefty price tag: $3.5 million.

The cocaine baron brought a small number of the African beasts to Colombia in the late 1980s. But after his death in 1993 the animals were left to roam freely in a hot, marshy area of Antioquia department, where environmental authorities have been helpless to curb their numbers which now stand at 150 animals.

Authorities said they plan to capture and move nearly half of the hippopotamuses in the coming months, with 10 bound for the Ostok Sanctuary in northern Mexico and 60 destined for an as-yet unnamed facility in India.

"The whole operation should cost around $3.5 million," Ernesto Zazueta, owner of the Ostok Sanctuary, told reporters.

He and governor Anibel Gaviria, of the Colombian region that is home to the hippos, say they plan to lure the animals with bait into pens where they will remain confined before being put in special crates for the transfer.

Colombia had tried a sterilization program to control the population, but it failed.

The environment ministry declared the hippos an invasive species last year, which opened the door to an eventual cull.

But the hippo transfer plan is seen as a life-saving measure.