By FRANCES ROBLES

Colombian authorities said they seized up to 66 pounds of low-grade uranium hidden off the side of a road in southern Bogotá on Wednesday, which the Colombian Defense Ministry said belonged to FARC guerrillas.

The Defense Ministry said the discovery adds weight to the evidence found in a laptop belonging to slain guerrilla leader Raúl Reyes, which showed the rebels were interested in buying and selling the uranium on the international underground market.

But the 30 kilograms of uranium found in plastic bags dug about three feet from a road in southern Bogotá was ''impoverished,'' the ministry said, and in that state could not have been used to make a radioactive bomb. Authorities were waiting for further analysis to determine how dangerous the material found really is, Armed Forces commander Freddy Padilla told a news conference late Wednesday.

It was not clear if Colombian authorities meant that they had found depleted uranium, which is the residue left after the mineral is processed to make nuclear energy or nuclear weapons. In its natural state, uranium has low radioactivity and it has to be enriched through a sophisticated process to generate nuclear energy or to make nuclear weapons. According to Colombian daily El Tiempo, the country does not possess the technology to enrich uranium.

The Colombian government has used details of an alleged deal, to buy up to 50 kilos of uranium at $2.5 million a kilo, found in emails on Reyes' computer to prove the Revolutionary Armed Forces of Colombia, or FARC, was planning to enter the international terrorism trade from its sanctuary set up in the jungle about one mile from the Colombia-Ecuador border.

A ministry statement Wednesday said that on March 20 informants gave military intelligence officers a sample of uranium allegedly acquired by FARC rebels. Mining experts analyzed the sample and on Tuesday confirmed it to be ''impoverished'' uranium.

The informants led the military to the rest of the stash in Pasquilla, a district in Bogotá's Comuna 20 neighborhood, the ministry said. The uranium was found Wednesday, hidden near the road that leads to San Juan de Sumapaz, a longtime rebel stronghold.

RCN TV showed footage of jeans-clad authorities pulling white cloth bags out of the brush off the side of a road.

Two pieces, one rectangular and another round, each about 33 lbs, were found covered in dirt, Padilla said.

'According to the informants, it's the material the FARC was negotiating that appears in Reyes' seized computer,'' Padilla said. ''The seizure is of great benefit, because it prevents the FARC from counting on this kind of material'' which it has wanted since 2005, he said.

He said the material was transferred to the mining ministry for more analysis on where it came from.

Padilla added the informants were people close to ''Belisario'' whose name appeared in Reyes' computer as the person charged with finding the radioactive material. Belisario, Padilla said, is not a guerrilla but rather a business contact.

Word of a possible effort by Colombian rebels to acquire uranium was first revealed earlier this month when the Colombian National Police rifled through one of several computers found at Reyes' bombed camp.

Some experts questioned the veracity of the emails, saying it was unlikely the FARC was engaged in such a business.

One of the computers contained a Feb. 16 e-mail discussing a deal to buy uranium, which can be used to make dirty bombs in which conventional explosives disperse radioactive materials. The emails suggested that the rebels may have intended to sell the uranium to a third party, rather than use it themselves.

''Another of the themes is the one on uranium,'' said the e-mail allegedly written by a man identified as Edgar Tovar to Raúl -- an apparent reference to Reyes, the FARC's No. 2 man.

''There's a man who supplies me with material for the explosive we prepare, and his name is Belisario and he lives in Bogotá,'' the note reads. ``He sent me the samples and the specifications and they are proposing to sell each kilo for two and a half million dollars, and that they supply and we look for someone to sell to, and that the deal should be with a government that can buy a huge amount. They have 50 kilos ready and can sell much more.''

Colombian Vice President Francisco Santos later said the note proved the FARC was ``negotiating to get radioactive material, the principal base for making dirty weapons of destruction and terrorism.''

''This shows that these terrorist groups ... constitute a grave threat not just to our country but to the entire Andean region and Latin America,'' he added.

The FARC has denied any uranium deal.

''Only developed nations like the United States and others have the conditions and the technology required to process uranium, not a guerrilla movement that still fights for people's dignity with rifles and even sticks,'' a FARC statement previously published by the Colombian media said.

Miami Herald Special Correspondent Jenny Carolina González contributed to this report. For updates, go to MiamiHerald.com/americas.