March 27 (Bloomberg) -- Colombian authorities are investigating what the country's biggest guerrilla group planned to do with 30 kilograms (66 pounds) of depleted uranium seized in a raid on the outskirts of Bogota.

General Freddy Padilla, head of Colombia's armed forces, said in a news conference yesterday that authorities were led to the buried cache by informants linked to an arms dealer named on the computer of slain rebel leader Raul Reyes. The find supports intelligence that the Revolutionary Armed Forces of Colombia, or FARC, were trying to get uranium since 2005, Padilla said.

``It's exactly the same material listed on Reyes' computer,'' Padilla said. ``Why the FARC were so anxious to obtain this material we still don't know.''

The seizure of the uranium underscores the value of intelligence gleaned from a half-dozen laptops the military captured from the FARC this month and shows how the underground operations of the 44-year-old insurgency are crumbling. Colombia used data from Reyes's hard drives, taken after a lethal cross- border raid into Ecuador, to implicate the governments of Venezuela and Ecuador in supporting the rebels.

Colombia's Vice President Francisco Santos said earlier this month that evidence on the laptops showed the FARC was seeking 50 kilograms of uranium to build dirty bombs, conventional explosives used in conjunction with radioactive materials.

Health Risk

The depleted uranium, found yesterday in a rural area outside the city, poses no health risk and can't be used to build a dirty bomb, said Charles Ferguson, a nuclear affairs analyst at the Council on Foreign Relations in Washington. A video released by the Colombian military showed the metal had a slow radiation rate of 1.5 Microsieversts per hour, he said.

``You could stand next to this material for days and nothing would happen to you, unless you dropped it on your foot,'' said Ferguson.

Possible uses for the FARC might include making armor- piercing conventional weapons or an ingestible poison, Ferguson said. Less likely, the metal could be used as a shield while handling more potent radioactive materials that would be used to make a dirty bomb.

U.S. State Department spokeswoman Nicole Thompson said the U.S. is ``deeply concerned'' by the seizure. ``We hope Colombian officials conducting this investigation will be able to determine the FARC's intended use of the uranium,'' she said.

The U.S., Canada and the European Union classify the FARC as a terrorist group.

`Stronger Rocket'

Mario Ballesteros, head of the state-run geology institute Ingeominas, said a study of the uranium, its possible uses and health risk would be presented on Friday, EFE news agency reported today.

``The FARC may have wanted this material to build a stronger rocket that destroys the president or a minister's armored car, not create a weapon of mass destruction,'' said Cesar Restrepo, from Bogota's Security and Democracy Foundation.

Padilla said informants he didn't identify, who are close to an alleged arms supplier Reyes called ``Belisario,'' led the military to the uranium. Authorities are investigating the origin of the material, he said.

Embossed on the two metal lodes, in English, was the warning ``Caution: Radioactive Material. Depleted Uranium,'' according to the military's video.

The computer files already led authorities in Costa Rica on March 17 to uncover $480,000 in cash at a guerrilla safe house. Authorities said the files were also useful in tracking down in Thailand suspected Russian arms dealer Viktor Bout.

``Reyes's computers are proving to be a gold mine, everything listed on it that President Hugo Chavez says are lies is proving true,'' said Restrepo.

Venezuela's President Hugo Chavez has said evidence on Reyes's computers showing he funneled $300 million to the FARC was a fabrication.

``This computer could say anything,'' he said during a visit today to Brazil.

To contact the reporter on this story: Joshua Goodman in Bogota at Jgoodman19@bloomberg.net

Last Updated: March 27, 2008 19:03 EDT