Katy Perry & John Mayer Go to a Strip Club in Vegas

Caught in the Act

09/10/2012 at 10:30 AM EDT

Looks like Katy Perry and John Mayer were waking up in Vegas!

The on-again off-again couple were spotted in Sin City early Sunday morning. With a group of friends, the duo spent their night out at Spearmint Rhino ... a strip club!

"They were together in a group," an onlooker tells PEOPLE. "As for whether they got dances, they were in a strip club ... you do the math."

The group had so much fun, they stayed until 5 a.m.

Earlier in the evening, Perry and Mayer checked into the Wynn Hotel together. It appears as if the "Wide Awake" singer met Mayer in Vegas, as he was seen having dinner at Palm's N9NE Steakhouse with two friends on Friday. Mark Gray