SALT LAKE CITY — The University of Utah has put together a panel of doctors and medical ethicists to find out how a convicted felon working at a fertility clinic two decades ago replaced a patient’s sperm with his own and fathered a woman who is now 21.

Taking full responsibility for the switch that occurred in 1991, University of Utah Medical Group CEO Sean Mulvihill on Wednesday promised as complete an inquiry as possible.

“This is a shocking story for all of us,” Mulvihill said. “We want to make sure that people are reassured that the policies and practices today make it inconceivable that the same sort of thing can happen today.”

The university has confirmed that Thomas Lippert, an employee of the private clinic that closed in 1998, is the biological father of the woman who now lives in San Antonio with her family.

They don’t know why or how his sperm samples got switched with the father’s, and set up a hotline and website for anyone else who visited the clinic between 1988 and 1993, when Lippert worked there.

About 15 people have called a hotline that the university set up earlier this month, and a couple of families are considering paternity tests. So far, there are no other known cases of Lippert fathering children without the family’s knowledge. Complicating matters is the fact that most of the records from the lab are gone, and Lippert and the former clinic director have died.

As many as 1,000 people may have gone to the clinic while Lippert worked there, said Mulvihill, but school officials can’t contact them all because of the missing records.

The woman fathered by Lippert, Annie Branum, says the discovery has forced her to rethink who she is. Her family stumbled upon the information while using widely available DNA tests to trace their family roots online. The results showed Annie Branum’s DNA didn’t match her father’s.

The website led them to a second cousin who had also used the DNA testing. They tracked her down, and she turned out to be Lippert’s cousin. She told the Branums that Lippert was a sperm donor who lived in Salt Lake City.

A DNA test of Lippert’s 99-year-old mother confirmed that she was the daughter’s biological grandmother.

The Branums, who didn’t return calls Wednesday, have previously said the university didn’t do enough with the information they gave them, accusing school officials of stonewalling to hide a wider scandal. They now live in San Antonio.

The university started investigating in April 2013, after the family told them what they had discovered. But officials concluded the clinic was private and closed the inquiry.

Since then, Mulvihill said, it’s become clear the clinic, Reproductive Medical Technologies, was more closely associated with the university than officials originally believed.

They shared space, staff and administrative oversight with a university clinic, and several of the key doctors in the lab were university faculty. Lippert worked at both labs as a medical technician who handled sperm samples.

Officials reopened the inquiry in October, and have dug up boxes of records.

No one knows what might have motivated Lippert, who in 1975 took a plea bargain on kidnapping and other charges for subjecting a Purdue University female student to electroshock behavioral modification techniques in a so-called “love experiment.”

Records show he initially received positive performance reviews from superiors. His behavior and performance deteriorated around 1993. Mulvihill wouldn’t provide details.

The university hopes the in-depth investigation brings answers. The panel includes three University of Utah doctors and a medical ethicist from the University of Wisconsin, to ensure the integrity of the review, he said.

Results of the review, which they hope will be done in three months, will be shared with patients and the public.

“We take responsibility for this situation and the uncertainty it has caused,” Mulvihill said.