43-year-old Perarivalan was lodged in the high security block.
A life convict in the Rajiv Gandhi assassination case, AG Perarivalan, who was brought to Chennai from Vellore central prison, on Monday underwent medical tests at Rajiv Gandhi Government General Hospital (RGGGH) here to determine his illess related to an infection.
He underwent ultra sound, echocardiogram, blood and urine tests besides a culture (urine) sensitivity test, doctors at the RGGGH told reporters.
It may take upto three days to get the results of culture sensitivity test, they said.
On June 6, Perarivalan was shifted to Puzhal Central Jail in Chennai from the Vellore prison to enable him get medical treatment for an illness linked to an urinary tract infection.
Doctors at the Vellore General Hospital had referred him to the RGGGH for speciality treatment.
After the tests, Perarivalan was taken back to Puzhal jail where he will remain for the next few days till such time all the results of medical tests emerge and based on the opinion of doctors.
"The extent of his stay here (Puzhal jail) will depend on what doctors say based on his test results," a top jail official told PTI.
Last year, the Supreme Court had commuted the death sentence of three, including Perarivalan in the Rajiv Gandhi assassination case, to life imprisonment.
Perarivalan was arrested in 1991 and has since then been lodged in Vellore Central prison.