Michael Bloomberg's presidential campaign is ending its relationship with a vendor amid reports that the vendor used prison labor for campaign work. First reported by The Intercept and confirmed to CBS News by a Bloomberg campaign official, the campaign, through a third-party vendor, contracted the services of ProCom, a New Jersey-based company that runs call centers out of at least two prisons in the state of Oklahoma.

According to the Intercept, incarcerated women in the Oklahoma minimum-security women's prison, Dr. Eddie Warrior Correctional Center, made calls on behalf of the Bloomberg campaign to California voters.

"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."

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The campaign would not disclose the name of the third-party vendor that hired ProCom or how much the campaign paid the vendor.

Matt Elliott, a spokesperson for the State of Oklahoma Department of Corrections, tells CBS News that vendors contract with his department through Oklahoma Correctional Industries for call centers. Some of the calls include "conducting surveys, selling subscriptions and making campaign calls all while reading from a script." Elliott says the projects provide inmates with "excellent work opportunities," and that whether inmates are required to identify themselves as inmates is up to the vendors.

"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," Elliott said. "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."

A spokesperson for ProCom has not yet responded to a request for comment by CBS News.

A late entry into the field, Bloomberg, the former mayor of New York and a prominent businessman, is self-funding his campaign and refusing to take donations. His wealth is estimated at over $50 billion. Bloomberg, who is taking a non-traditional approach to campaigning, is skipping the first four early-voting states and diverting significant resources to the Super Tuesday delegate-heavy states like California.