The Houston Public Library has issued an apology after a registered sex offender was allowed to entertain children during the library's highly controversial program called "drag queen storytime."

What are the details?

The library announced last Friday that a review of its volunteers revealed Albert Alfonso Garza never submitted a background check before being allowed to entertain children during "drag queen storytime," KTRK-TV reported.

According to the Houston Chronicle, Garza was convicted of aggravated sexual assault of an 8-year-old child in 2009.

He was last seen entertaining children at a Houston-area library last September. He will not be allowed to return, the Houston Public Library said.

"In our review of our process and of this participant, we discovered that we failed to complete a background check as required by our own guidelines. We deeply regret this oversight and the concern this may cause our customers. We realize this is a serious matter," the library said in a statement, KTRK reported.

We are taking the appropriate action to ensure that the status of every participant in every program throughout our system is verified. We will continue to review our process to ensure that this cannot happen again," the statement continued.

To re-assure the public, the library also explained that "drag queen storytime" participants are not allowed to be alone with children. Additionally, HPL said it has never received a complaint about inappropriate behavior.

What is drag queen storytime?

The controversial program, which allows drag queens to read to children, takes place at the Freed-Montrose library and is "part of a national program that aims to promote love and acceptance," according to KHOU-TV.

Opponents of the program filed a lawsuit against the city of Houston and Mayor Sylvester Turner last October with the aim of stopping the program. A judge dismissed the lawsuit in January.