BOGOTA -- Colombian police have seized property and bank accounts worth 1.3 trillion pesos ($329 million), proceeds from the sale and export of stolen crude oil, officials said on Thursday.

The national police and Interpol have carried out seven investigations since 2016 into the theft and smuggling of oil by four criminal organizations, a police statement said. The enterprise managed to export 975,000 barrels of crude between 2020 and 2021, it said.

Thousands of barrels of oil are stolen from Colombia's pipelines each day, often by criminal gangs who refine it into a bootleg fuel known as pategrillo for use in making cocaine or running machinery in illegal mining.

The practice of perforating pipelines and storing oil in pools in the jungle is an environmental disaster, Reuters reported last year, after visiting clandestine refineries in Narino province.

"Businessmen and technicians are involved and the National Liberation Army (ELN) is clearly linked due to its illegal activities of hydrocarbon theft and attacks against the Cano Limon-Covenas pipeline," said independent energy analyst Katherine Casas, referring to a rebel group that regularly bombs pipelines.

Police seized houses, apartments, boats, vehicles and four refineries earlier this week, as well as 17 bank accounts - Colombian and international - valued at 20.3 billion pesos ($5.14 million).

To sell the stolen oil, criminal groups mixed it with legally-bought crude so it could be exported via front companies, police said.

Colombia's majority state-owned oil company Ecopetrol (ECO.CN) was the main victim of the scheme, costing it 60 billion pesos, police added.

"From 2013 to 2023, 9,925 illegal valves have been removed from Ecopetrol Group's transportation systems," the company said in a statement, adding that it was working with the government and security forces to tackle illegal operations.

The gangs stole crude from Colombia's Cano Limon-Covenas pipeline which runs parallel to the border with Venezuela. It was processed elsewhere before being sold nationally or smuggled to the Pacific port city of Buenaventura and exported.

Furthermore, "large quantities" of light Venezuelan crude were brought into Colombia before being mixed with Colombian oil and exported via the Cano Limon-Covenas pipeline, the statement said.