He is receiving treatment at the hospital under heavy police guard.
There were strong fears on the health and whereabouts of Mwanaka after the MDC, lawyers and his relatives could not locate him at any of the police stations in Harare since his arrest yesterday.
He is part of eight MDC members who were arrested at Harvest House yesterday when anti-riot police officers stormed the building. The others are detained at the Harare Central Police Station but no charges have been brought against them.