The BBC reported Thursday the U.S. military commander for the region said recently it was 90 percent certain Moore and four other British nationals taken hostage in Iraq were actually held in neighboring Iran.
While Moore was freed Wednesday after 2 1/2 years of captivity, three of his fellow hostages were killed by their captors and officials suspect the fifth hostage was also slain.
The Guardian reported an unnamed former Iranian Revolutionary Guard member said "it was an Iranian kidnap, led by the Revolutionary Guard, carried out by the al-Quds brigade."
However, a United Kingdom Foreign Office spokesman said while there has been speculation the hostages may have been held in Iran, there is no proof the Iranian government was involved in the abductions.
"Iran, of course, has an influence in Iraq, but we have no evidence to substantiate claims of direct involvement in this case," the spokesman told the BBC.
Sami al-Askari, senior adviser to Iraqi Prime Minister Nouri al-Maliki, also denied allegations Iran was involved in taking the Britons hostage, saying his negotiations for the hostages' release took place in Iraq.