Jayalalithaa was admitted to hospital after she had fever and suffered from dehydration.
Tamil Nadu Chief Minister J Jayalalithaa, admitted to Apollo Hospital late Thursday, was under observation and on normal diet, the hospital said.
In a statement issued on Saturday, Apollo Hospital said: "The Honourable Chief Minister of Tamil Nadu is under observation. Honourable Madam is on normal diet."
Jayalalithaa had fever and suffered from dehydration on Thursday.
The Chief Minister "has no fever now and is taking normal diet", a hospital statement said on Thursday.
However, it is not known when she will be discharged from the hospital.
Ministers as well as supporters of the AIADMK leader were assembled in droves outside the hospital praying for her recovery.
News agency ANI reported that some AIADMK party cadres held special prayers in Chennai for Jayalalithaa's speedy recovery.
Earlier in the day, some erroneous reports suggested that the Tamil Nadu Chief Minister would be flying to Singapore.
Later, AIADMK leader, CR Saraswathi, clarified: "She is very healthy, no problem at all. This (reports that TN CM will travel Singapore for treatment) is just a rumour."