Former Prime Minister Lee's condition has worsened, the Prime Minister's Office (PMO) said in a statement.
Lee, 91, is now is his 45th day at the hospital, having been admitted on February 5 with severe pneumonia. He has been on mechanical ventilation since February 21.
Lee's condition took a turn for the worse on Tuesday, when he contracted an infection. On Wednesday, the PMO said his condition had "deteriorated further" and that he remained "critically ill" in the ICU.
As prayers and well wishes kept coming in from Singaporeans, for the founding father of modern Singapore, a special area was also set up for well-wishers to leave cards, flowers and gifts for him at SGH.
Lee was the first Prime Minister of Independent Singapore till 1990.
Singapore's economic and development success is attributed to Lee's strong leadership during the three decade as Prime Minister.