The newspaper said the facility, known as Location C, was Iraq's only internationally sanctioned storage site for nuclear material and thus was a potential prize for for anyone seeking to steal radioactive substances.

Iraqi Republican Guard troops abandoned the site late last week as US troops approached the nearby Tuwaitha nuclear research center south of Baghdad, the report said.

Looters soon cut Tuwaitha's electric fences and began ransacking homes and offices, hauling off television sets, carpets and other valuables.

According to The Los Angeles Times, US Marines who entered the chaotic complex last weekend did not realize Tuwaitha's significance.

US combat engineers finally secured Location C on Wednesday, after a State Department counter-terrorism task force warned the Central Command of the danger, the paper said.

It was not clear Thursday if special US weapons teams had reached the site, and US military officials said they did not know if anyone had breached the steel doors and removed any of the 500 tonnes of unprocessed uranium and uranium dioxide, 1.8 tonnes of low-enriched uranium and radioactive devices that were stored at the site, The Times reported.

SPACE.WIRE