"But she is under close monitoring."
Tandon said some tests including MRI, CT scan and blood examinations had been done and some more tests were likely to take place on Thursday.
Banerjee was admitted to the clinic shortly after she returned from Delhi on Wednesday afternoon. She was driven straight to the clinic from the airport.
The decision to admit her was taken after the chief minister complained of pain on both shoulder joints, neck, back mainly over left lumbosacral region and left knee joints.
Banerjee was examined on Tuesday by doctors at AIIMS in Delhi who advised her to get admitted for observation.
SFI members had blocked the chief minister's passage in the Planning Commission in Delhi on Tuesday and manhandled state finance minister Amit Mitra while they were going to attend a meeting.
The chief minister subsequently fell ill and was administered oxygen while Mitra was put under observation at AIIMS.