Sabha in Deep Sahara

Sabha, Libya (CNN) -- Amilitary site containing what appears to be radioactive material has been uncovered by revolutionary forces near the southern Libyan city of Sabha.

Military forces loyal to the country's National Transitional Council took a CNN crew Thursday to the site, not far from Sabha in the Sahara desert. The crew saw two warehouses there, containing thousands of blue barrels marked with tape saying "radioactive," and two or three plastic bags of yellow powder sealed with the same tape.

The material has not been confirmed as being radioactive, but in 2004 the International Atomic Energy Agency (IAEA) confirmed that the Libyan government had yellowcake stored in Sabha.

Yellowcake is processed uranium ore that can, after extensive refining, be used to produce enriched uranium for nuclear purposes.

Fighters entered Sabha, long regarded as a pro-Gadhafi stronghold, on Wednesday afternoon and initially met no resistance, officials said.

The military site outside the city, found Wednesday night, is now guarded by about a dozen lightly-armed revolutionary fighters. It does not appear to have been left unfrequented for long.

Protective suits were found hanging in offices that appear previously to have belonged to the Libyan government, along with rubber gloves, devices for measuring radioactivity and various military documents.

The site also contains boxes of old surface-to-air missiles and rockets.

A field commander for the revolutionary forces said the NTC was very keen for the international community to come in, identify the suspect material and take it to a place of safekeeping.

The forces fear it could cause an environmental disaster if it were to explode during fighting, the commander said.

John Pike, a defense expert at Global Security, told CNN the elderly rockets might pose a greater threat to safety than the suspected radioactive material.

The discovery of the material is not a surprise, he said, as the IAEA had established that yellowcake was at the site and was being decommissioned. The current status of the material is not known, however.

An IAEA report from 2008 states that Libya had declared that between 1978 and 1981 it imported 2,263 tonnes of uranium ore concentrate, which was being stored at Sabha.

However, plans to build a uranium ore concentration and conversion facility in the Sabha area were not carried out, the report says.

Elsewhere, revolutionaries have taken control of the southwestern town of Ubari, chasing Moammar Gadhafi loyalists from the area as Libya's new leaders continued to gain momentum, NTC field commander Al-Amin Shtawi said Thursday.

The announcement comes days after the NTC received the significant milestone of being recognized by South Africa and the African Union as Libya's legitimate rulers. Troops loyal to Libya's new leaders have been putting pressure on several regime holdout cities in recent days.

Along with Thursday's military action in Ubari, fighters have also clashed with Gadhafi loyalists in the northern town of Bani Walid and in Sirte.

Ahmed Bani, an NTC military spokesman speaking in Tripoli Thursday, said revolutionary fighters had encountered mercenaries who appeared to be from Chad or Niger, and had uncovered caches of weapons and military supplies.

He said most of the towns in southern Libya had been "liberated" from Gadhafi loyalists and that revolutionary forces would continue to fight for control of Bani Walid. "Our revolutionaries won't lose hope," he said.

Despite not yet having complete control over the entire country, the NTC says it is planning on how to set up a new government.

Elamin Belhaj, a senior member of the NTC, told CNN Wednesday that the formation of a Libyan government will not be announced until anti-Gadhafi forces control the borders of the country and liberate the three cities of Bani Walid, Sirte and Sabha. That effort could take up to one month, he said.

After liberation, the NTC will create an interim government by appointing a prime minister who will be responsible for forming the government.

The prime minister will decide how many ministers will be in that interim government, but he must return to the NTC for approval of that government. That government will create a new constitution that will be put before the Libyan people for approval in a referendum.