CHICAGO (CBS) — Illinois Attorney General Lisa Madigan’s office has opened a civil rights investigation into a bus company serving University of Illinois students, for an advertisement that offended Chinese students, and which the company has since acknowledged was “grotesquely xenophobic.”

Madigan’s office said it wants to determine if Champaign-based Suburban Express, Inc., discriminates against customers on the basis of race and national origin.

The investigation was prompted by an email advertisement directed at University of Illinois students traveling between Champaign-Urbana and the Chicago area during the holidays.

The ad stated “passengers like you…you won’t feel like you’re in China when you’re on our buses.”

The university criticized the ad as “bigoted,” and the company initially issued an apology that only compounded its problems.

“We made a remark based on the fact that our competitor mostly handles Chinese international students,” the apology read. “The remark is being interpreted as a slap in the face of all non-caucasians for some reason, and that it [sic] not how it was intended.”

The company has issued a second apology, calling the ad “grotesquely xenophobic in nature.”

“There is no benefit, by any measure, to excluding any demographic and we apologize for this indefensible statement,” the company said in a Facebook post.

The second apology also acknowledged the first was “harmful insofar as it tried to excuse a wrongfully nationalist statement.”

“The sarcastic tone and disagreement with the University of Illinois’ inclusive practices are just as offensive and wrong and we apologize with great shame,” the second apology stated.

The attorney general’s office has subpoenaed documents from the company to determine if its policies and practices follow the Illinois Human Rights Act.

Suburban Express said it would cooperate with the investigation, as well as Chicago Ald. Ameya Pawar’s call for a public hearing.

“It is our company’s mission to provide safe, reliable, and fair transportation for all students. We will work endlessly to ensure this,” the company stated. “As this year concludes and a new year approaches, we invite all people to work with us and take this incident as an opportunity to get to know us as we work hard to reform our practices. We will strive to work swiftly and professionally to make amends and to adhere to the highest standards of conduct from this moment forward. We only hope you can trust this will never be repeated, and that we will only do better in the future with all students and customers.”

Madigan’s office said anyone who wants to file a complaint in the case can call their civil rights hotline at 877-581-3692.