(CNN) Paul Manafort is in the hospital after suffering a heart ailment while in prison, a source familiar with the matter said Tuesday.

The former Trump campaign chairman is serving a seven-and-a-half-year sentence in a Pennsylvania prison for financial crimes that stemmed from special counsel Robert Mueller's investigation.

He was admitted to the hospital on Thursday, lawyer Todd Blanche said. Blanche said Manafort was in stable condition, though he said that he, along with Manafort's family, was being kept in the dark about the full extent of Manafort's medical condition.

A spokeswoman for the Federal Bureau of Prisons declined to comment, citing safety and privacy concerns for inmates.

News of Manafort's medical status, which was first reported by ABC News , came the same day that his longtime deputy, Rick Gates, was sentenced on charges also born from the special counsel's probe.

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