Justin Bieber partied with a mystery blonde in New York last night (31.01.14).

The 'Confident' singer's arrival in the US was delayed at the airport where customs officials searched his private plane for marijuana and held him for five hours of extended questioning - as he currently has two criminal cases pending against him - but he made it to the Maxim Big Game Weekend party.

The 19-year-old star had been turned away from three previous events because he wasn't 21, before being sneaked into the back entrance of the Maxim event just before 1am today (01.02.14).

Justin - who is rumoured to be dating Chantel Jeffries - arrived with an entourage of around 15 people and didn't leave the party until its very end at 4am.

A source told AccessHollywood.com Justin ''invited a blonde girl into his booth. She accepted his invite, stayed with him for the duration of the evening, then eventually left with [him].''

Other sources say the singer was in a private booth for around 20 minutes before anybody realised he was at the party.

Security guards kept a watchful eye on the singer - who is in town for the NFL Super Bowl in New Jersey tomorrow (02.02.14) - to make sure he wash 't drinking and stopped partygoers from taking photos with cameras or phones, although one picture has surfaced of Justin showing his middle finger at a cameraman he had spotted.