La Lohan was joined by mother Dina and inseparable gal-pal Samantha Ronson, among others, at the club inside the Roosevelt Hotel.

Get all the details of the birthday bash inside!

"Someone's coming forward saying something that is not verified or anything," Michael Lohan said in an interview with Access Hollywood's Billy Bush, scheduled to air tonight on "The Billy Bush Show."

On Friday, OK! Magazine ran a report claiming that Michael Lohan had admitted to the publication that he engaged in a relationship with a woman, while he was undergoing a separation from now ex-wife, Dina Lohan, which resulted in a pregnancy.

Find out what Michael revealed to Billy inside!

According to OK! magazine, Michael Lohan has admitted to fathering a child with another woman while married to Lindsay's mom, Dina.

"Years later [the woman] contacted me, convincing me that I was the only person she was with and that she had my child," Michael reportedly told OK!.

However, in an interview earlier today with Access Hollywood's Billy Bush for Access and his radio program, "The Billy Bush Show," Michael believes the other woman is simply after his money.