Colombian rebels may have acquired government-supplied medical drugs in Brazil, possibly from health workers, to treat a disease plaguing their forces, Brazilian federal police said on Thursday.

Nearly 3,000 capsules of the scarce drug Glucantime were recovered after three men thought to be Revolutionary Armed Forces of Colombia (FARC) guerrillas had a boat accident last October in Brazil’s far northwest Amazon, federal police said.

“We are almost certain they were FARC ... this drug is worth its weight in gold to the guerrillas,” said superintendent Sergio Fontes, who is leading the investigation.

The incident, which police only disclosed this week, was the latest sign of possible FARC activity in Brazil, which borders Colombia and is neutral in the four-decade war between the Marxist rebel army and Colombian armed forces.

The Amazon boat accident was near the town of Sao Gabriel da Cachoeira - a suspected supply point for FARC rebels about 90 miles (140 km) south of the Colombian border.

In previous years police have found huge cargoes of goods ranging from frozen chickens to flip flops near Sao Gabriel which they suspect were destined for the FARC’s 17,000 rebels.

Police recovered the launch, drugs and over 9,000 rounds of military-use ammunition but did not capture the men.

Glucantime is used to treat Leishmaniasis - illnesses caused by a parasite passed by insect bites. It is so common among the FARC it is known in Colombia as “the guerrilla disease.”

Diseases range from skin sores to fever and swelling of the spleen, liver and glands, which can be fatal if untreated.

The sale of Glucantime is prohibited in Colombia where only the government supplies the drug. The sole supplier of Glucantime in Brazil is the federal government.

Police doubt there was an “institutional” decision by health authorities to help the rebels. They are investigating whether health workers sold the drug directly to the FARC.

“It’s unthinkable the government made a donation to the FARC,” Brazil’s health minister Humberto Costa told reporters.

Brazilian news magazine Veja this month revealed the country’s intelligence agency received a report that the ruling Workers’ Party got a $5 million donation from the FARC for its 2002 presidential campaign. The agency confirmed the existence of the report but said it was a rumor and the case was closed.