Olsen -- then known as "G-Reg" -- recorded the song "7th Floor Crew" with a rap group of the same name in 2003 while a college freshmen. The group reportedly named themselves after the seventh floor of a University of Miami dormitory, the Chicago Sun-Times reported Tuesday.
The song sparked a brief controversy at the school when it came to light in 2005 and the school's athletic director, Paul Dee, issued a formal apology.
However, Olsen's new NFL career has brought new attention to the song and its lewd lyrics.
Bears communications director Scott Hagel said the recording was a thing of the "in the distant past" and was "a one-time issue."
Olsen himself offered an apology through the team.
''As a freshman, a few of my friends and I recorded a song that was written for us," Olsen said. "It was an immature mistake on my part, and I certainly recognize it was wrong. I am not proud of what we did and have become a more mature person over the past three years."