Tamil Nadu Chief Minister J Jayalalithaa's situation is "extremely grave", said British specialist Dr Richard Beale, who has been assisting doctors at Chennai's Apollo Hospital in treating Ms Jayalalithaa since she was admitted in September.
"The situation is extremely grave, but I can confirm that everything possible is being done to give her the best chance of surviving this shocking event," said Dr Beale. He also said in his statement that "unfortunately, and in spite of the progress she had made, her underlying health conditions inevitably meant that the risk of further problems always remained".
Sangita Reddy of Apollo Hospital has tweeted that, "Despite our best efforts, our beloved CM remains in a grave situation," and in a statement the hospital said that Ms Jayalalithaa continues to be on an extracorporeal membrane heart assist device or ECMO, a life support system that aids heart and lung functioning, and other life support and is being monitored and treated by experts.
The hospital has denied a statement by the chief minister's party earlier today that she had a heart surgery this morning.
While Dr Beale said he is in close touch with doctors at Apollo, a team of four doctors from Delhi's prestigious AIIMS will also arrive in Chennai this evening and will join in her treatment.
The state's Governor C Vidyasagar Rao was at the hospital a while ago for his second visit since last night. He had reportedly briefed Home Minister Rajnath Singh after last night's visit and told him that law and order in the state is under control.
Hundreds of Ms Jayalalithaa's supporters have been outside the hospital overnight, and the crowds are now swelling after the latest statements from doctors, with people wailing and weeping and praying for their leader's recovery.
They had been assured by the AIADMK this morning that the chief minister was better. "There was an angio procedure this morning. Doctors say don't worry, Amma will be fine," AIADMK spokesperson CR Saraswathi had said, adding, "we are telling cadres don't worry. God is with Amma, she will come back. Definitely she will be ok."
There is heavy security outside the hospital, with barricades put up. The police, on high alert, have blocked roads leading up to the hospital to avoid congestion.
AIADMK lawmakers and ministers will meet at the hospital at 6 pm, sources said. Top bureaucrats are also at the hospital as are Ms Jayalalithaa's close aides Sasikala and Sheela Balakrishnan, a former chief secretary and adviser to the chief minister.
Ms Jayalalithaa was admitted at the Apollo Hospital on September 22 and has been there since. Initially her party said she had dehydration and fever, but doctors later said she had an acute lung infection and was on respiratory support.
For several weeks, the hospital had reported much improvement in Ms Jayalalithaa's health and said she could decide when to be discharged. Her party said she was directing important decisions and had begun speaking.
On Saturday, the AIADMK had said Ms Jayalalithaa had been declared fully recovered by a team of doctors from AIIMS and would decide when to return home.