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Pictures of Justin Bieber partying with friends at a Houston nightclub is prompting an investigation into possible underage drinking. 

A rep for the Texas Alcoholic Beverage Commission tells a complaint has been filed, even though bar managers at NOX claim the 19-year-old singer was only drinking water. 

Officials say the bar's license could be in jeopardy if investigators conclude otherwise. 

Back in July a Chicago nightclub was slapped with a citation for allegedly serving the singer alcohol, though management at Bodi nightclub deny any laws were broken. 

Photo Credit Splash News