Meanwhile, US and Jordanian officials are examining Kuwait-born Muhammad Youssef Abdulazeez's trip to Jordan, looking for clues into what might have prompted him to open fire at a military recruiting office and a Navy-Marine operations center in Chattanooga on Thursday, killing four Marines and one sailor.
Media reports have suggested he also visited the small, energy-rich nation of Qatar on the same trip. But Qatar's government insisted his time in the country was limited to its gleaming international airport.
It said Abdulazeez changed planes at Doha's Hamad International Airport on his way from Amman, Jordan in November en route to the US.
Qatar has emerged as a major long-haul transit hub in the Middle East thanks to the rapid growth of government-backed Qatar Airways. Its new airport opened last year, a key piece of infrastructure ahead of its planned hosing of the 2022 World Cup.
Qatar is an important US ally in the Gulf that hosts a major US air base, though it has come under scrutiny for its links to Islamist groups, including Hamas and the Taliban. It insists it does not support terrorism.
Jordanian authorities, meanwhile, have been questioning relatives of Abdulazeez as part of an investigation into the time he spent in the kingdom last year, a government official said Tuesday. The official, who would not elaborate on the probe, spoke on condition of anonymity because he was not authorized to discuss details of the case with the media.