Justin Bieber has been allowed entry back into the US following his detention by customs officials on Thursday.

The troubled pop star was held for questioning for four hours after returning to the US from Singapore.

He was driven away in a van that had been awaiting his arrival at the airport but it was uncertain why he was held.

A member of Bieber’s entourage was left int he dark saying: "I have no idea what's going on in there -- we're just waiting. But it's been more than an hour and a half now..."

No official word has yet been given as to why Bieber was questioned but this isn’t the first time he has run into customs officials recently.

His private plane was searched back in November after he returned from South America.