The officials spoke on condition of anonymity yesterday because they were not authorised to speak publicly.
UN spokesman Stephane Dujarric wouldn't confirm the contractors' nationality but said they arrived on a UN aircraft from Djibouti on October 20 and were detained by "the authorities at the airport in Sanaa."
He said the two "are not UN contractors" but work for the company that manages the facilities that the UN is using in Sanaa.
The UN offices are at the US embassy, the officials said. US State Department spokeswoman Elizabeth Trudeau said: "We're aware of those reports. Due to privacy considerations, I'm not going to comment on them.