WASHINGTON (AFP) - One of two American contractors who were detained when they arrived in Yemen last month has died in custody, a US official told AFP on Tuesday.

Officials have been guarded in their comments about the case, citing privacy concerns, and the circumstances of the death are not yet clear.

Last month, the United Nations said two contractors working for a company that maintains a hotel in Yemen used by UN staff had been detained in Sanaa.

On Tuesday, United Nations spokesman Stephane Dujarric said: "We have been informed by the State Department of the death of one of the contractors.

"Obviously, we send our deep condolences to his family, to his wife, to his children," he added.

"The other contractor as far as I understand remains in custody, but I have nothing to share with you as to discussions that may be going on."

The pair had arrived at the airport on Oct 20 and were taken into custody by local authorities.

The US State Department has not publicly confirmed that the detainees are Americans, but has said it is "aware of reports" that two US citizens were taken.

Yemen is in a state of war between Huthi rebels and their allies, and a Saudi-led coalition supporting the official Yemeni government.

The United Nations is trying to broker a ceasefire.