DWTS stars out of control!

Former *NSYNC -er Lance Bass, dancer Maksim Chmerkovskiy and his fiancee Karina Smirnoff, along with Australian dancer Kym Johnson, laced a night of karaoke with a healthy dose of alcohol in Nashville on Jan. 19, according to eyewitnesses.

As these exclusive photos show, the foursome - in town for the Dancing with the Stars tour - kicked up their heels during an all-night karaoke fest fueled by vodka tonics, Red Bulls and Coors Lights.

The five-hour sing-along lasted until the Buckwild Saloon closed at 3 a.m., when the wild bunch stumbled into their chauffeur-driven cars, according to sources.

"Lance, Maksim and all the rest of them - including a large throng of Bass's buddies - were feeling no pain!" an eyewitness told The ENQUIRER.

"Around 10:30 p.m. the party was already in full swing. Lance kept running up out of the audience to sing karaoke, and Maksim, Karina and Kym joined him.

"They were stumbling around the small stage, trying to read the lyrics off a tiny teleprompter. And it didn't matter who was singing - heavy metal headbangers or country and western fans. You name it - they sang with them all!"

The group muddled their way through Britney Spears' hit "Oops!…I Did It Again," the *NSYNC song "Bye Bye Bye," along with "Gangsta's Paradise" by Coolio and "Big Poppa" by the Notorious B.I.G., the source divulged.

When closing time came, the dancers poured out of the bar, but not before putting on one final show, said the source.

"Lance and Maksim both straddled a saddle out in front of the saloon and started shouting, 'Yee-haw!'"

For all the pictures pick up the latest ENQUIRER.