DUBAI, United Arab Emirates (AP) — Iran seized a Vietnamese-flagged oil tanker in the Gulf of Oman last month and still hold the vessel off Bandar Abbas, two U.S. officials told The Associated Press on Wednesday.

One of the officials said Iranian Revolutionary Guard troops took control of the MV Southys on Oct. 24 at gunpoint.

A motive for the seizure remains unclear. Officials in Vietnam could not be immediately reached for comment. Ship-tracking data showed the vessel still off Bandar Abbas on Tuesday.

The two U.S. officials spoke on condition of anonymity as the information had yet to be made public amid ongoing attempts to restart talks in Vienna with Iran over its tattered nuclear deal.