Mike Sonko, the county governor of the Kenyan capital, Nairobi, has been taken from prison to hospital, health officials have confirmed.
They did not say what he is being treated for but said that he had been admitted and a prison guard is on watch.
He was in Kamiti Prison awaiting trial for money laundering and unlawful acquisition of public property.
He is accused of irregularly awarding tenders to his close aides, forging documents and misappropriating county funds.
He pleaded not guilty on Monday.
Mr Sonko is a divisive politician who has previously faced allegations of drug trafficking and money laundering, which he denied.
Recently prison authorities accused him of escaping from a maximum facility 20 years ago.
Mr Sonko’s bail application is due to be heard on Wednesday.