Colombian authorities seized 12 tons of cocaine worth an estimated $360 million in the country's largest-ever drug bust -- and they put the goods on display.

Four hundred anti-narcotics officers found the cocaine stored underground in four farms in a banana-growing region of northwest Antioquia province, near the border with Panama.

Officials said the drug belonged to the Clan del Golfo, an illegal armed group that has sought to take over drug trafficking operations in zones previously occupied by the Revolutionary Armed Forces of Colombia, or FARC.

President Juan Manuel Santos, surrounded by armed soldiers, walked on hundreds of packets of cocaine which had been laid out like a carpet at a police base.

“Thanks to a police operation with overseas intelligence, from friendly countries, the largest seizure in history was made,” he said, according to Reuters.

The seizure comes as the United States and the United Nations have raised concerns over an increase in coca cultivation. Both say coca and cocaine production surged last year in Colombia.

Santos, who leaves office next year, has pledged to send military and police to areas once controlled by FARC.

FARC rebels reached a peace agreement with the government last year that includes provisions to reduce coca production through voluntary and forced eradication.

Police said four people were arrested during the seizure.

El Clan del Golfo, or Gulf Clan, is led by fugitive Dairo Antonio Usuga, or Otoniel.

The United States has offered a reward up to $4.9 million for information leading to his capture or death.

Colombia is one of the world’s leading producers of cocaine, with output of around 910 tons per year, according to the U.S. Drug Enforcement Administration. Anti-drug police have confiscated 362 tons of cocaine this year.

The Associated Press and Reuters contributed to this report.