BEIJING, Nov. 29 (Xinhuanet) -- NASA engineers think it's no big deal for the International Space Station's crew or upcoming shuttle launch, but they are serious about tracking down a slight air leak in the Earth-orbiting habitat.

An inspection of a vestibule bridging the station's new Harmony connecting module and NASA's Destiny laboratory indicated a leak of about three pounds (1.3 kilograms) per day, NASA spokesperson Lynette Madison, of the agency's Johnson Space Center, told SPACE.com Wednesday. But whether the leak is genuine or merely a phantom signal has yet to be determined.

A close-up inspection of the vestibule seal by the station's three-astronaut Expedition 16 crew using an ultrasonic leak detector found no trace of a leak on Wednesday, Madison said. Studies of the station's overall internal pressure also found no signs of decay, she added.

Engineers first recorded the potential leak during a "fine" check this week to ensure Harmony is properly connected to its Destiny docking port, Madison said. A less sensitive, "gross" leak check performed earlier this month yielded no issues, she added.

Engineers plan to check the seals between Harmony and its shuttle docking port for leaks on Thursday, and may recheck the module's connection to the Destiny lab later this week, she added.

With its multiple berthing ports, Harmony is designed to serve as the anchor point for European and Japanese laboratories beginning with the European Space Agency's Columbus module set to launch next week.

(Agencies)