Democratic 2020 Presidential Candidate and billionaire entrepreneur Michael Bloomberg announced on Tuesday that his campaign is disassociating itself with the third-party labor contractor, Pro-Com, after learning that it exploited convicts from a prison call center.

The campaign employed the services of Pro-Com – a third party New Jersey-based contractor that runs call centers in at least two Oklahoma prisons – to source affordable campaign labor from a call center at the Dr. Eddie Warrior Correctional Center in Taft, Oklahoma.

The Dr. Eddie Correctional Center is a minimum-security all-female prison, with a capacity of around 900 women, who were routinely making campaign calls to California, for less than outside minimum wage and without benefits, on behalf of the campaign. “Inmates can receive $1.45 an hour working for call centers, working eight hours a day, five days a week. Inmates may work additional hours but only with permission from the director of Oklahoma Correctional Industries,” Mark Elliot, a spokesperson for the State of Oklahoma Department of Corrections, stated. “We believe this type of work helps prepare inmates for release, and these public-private partnerships give them an idea of and training in what to expect in the workplace later.”

“The use of prison labor is the continued exploitation of people who are locked up, who really have virtually no other opportunities to have employment or make money other than the opportunities given to them by prison officials,” Alex Friedmann, a managing editor of Prison Legal News and an advocate for incarcerated people’s rights, said.

Pro-Com co-founder, John Scallan, stated that his company pays the Oklahoma minimum wage of $7.25 an hour to the Oklahoma Department of Corrections, which in turn disburses salaries to incarcerated people employed at the detainee centers. The Department of Correction’s website lists the maximum monthly wage for detainees as $20 per month, but another policy document states there is a maximum wage of $27.09 per month.

Bloomberg said he became aware of the situation when a reporter telephoned him regarding the matter. “We only learned about this when the reporter called us, but as soon as we discovered which vendor’s subcontractor had done this, we immediately ended our relationship with the company and the people who hired them,” the campaign said in an email. “We do not support this practice and we are making sure our vendors more properly vet their subcontractors moving forward.”

Bloomberg, who Forbes ranked as the eighth richest American, has spent more on campaign ads in the past couple of weeks than his Democratic counterparts have spent all year. He is a self-made billionaire who put himself through John Hopkins and Harvard to become a partner at Salomon Brother’s, and later began his own company, which revolutionized the distribution of financial information and made him a billionaire. After entering the crowded race, for a long-shot bid for Democratic Presidential nominee, in November, Bloomberg’s campaign has already hired more than 200 staff members. It has also spent over $76 million in television advertisements.