Justin Bieber -- Jet Detained Because Of Pot Smell

5:45 PM PT We're told Bieber has just been released.

5:03 PM PT -- We were just told Bieber is still being questioned -- and everyone has ordered out for pizza. Cops tell us ... it's gonna be a while.

2:55 PM PT -- TMZ has learned Justin is now being held and questioned by U.S. Customs officials.

12:59 PM PT -- We're told all passengers were released. No drugs were found.

Justin Bieber's private jet touched down outside NYC for the Super Bowl -- and authorities immediately held him for questioning ... because of a strong odor of pot coming from his plane ... TMZ has learned.

We're told ... the plane was stopped after it arrived at Teterboro airport in New Jersey. As we told you ... Justin, his dad and some friends were traveling there for Super Bowl parties.

Sources tell us law enforcement is holding the plane ... because they think there may be marijuana on board. We're told the plane and the passengers are currently being searched ... but so far no pot has been found.

A source close to Bieber tells us, the passengers knew they'd be searched ... since they were flying into the U.S. from Canada.