At 2 am, his son Uddhav, emerged to tell hundreds of party workers, "Earlier too Balasaheb was in such a crisis. I have not lost hope. You too must not lose hope. All efforts are on. Please pray."
Earlier on Wednesday night, as the news spread of their leader's health, Sena workers gathered outside his residence 'Matoshree' in suburban Bandra, where security has been significantly increased.
Mr Thackeray's nephew, Raj, who was estranged from him till recently, was at 'Matoshree.' In 2006, Raj formed his own party, the Maharashtra Navnirman Sena or MNS.
Actor Amitabh Bachchan and his son Abhishek were among Mr Thackeray's late-night visitors. Mr Bachchan's kurta was torn according to some reports as he tried to make his way into the house through the huge crowd.
Mr Bachchan later tweeted, "Yes both Abhishek and me were injured with cuts, but are fine and back home ... the doctors at 'Matoshree' attended on us !"
Actor Sanjay Dutt and his wife Manyata also met Mr Thackeray's family late on Wednesday night.
A team of doctors stationed inside the house with nursing staff has been taking care of the Sena patriarch, who has been having breathing problems recently.
Last month, he could not attend his party's annual Dussehra rally in Mumbai, but addressed it through a video recorded message.
(With inputs from agencies)