The Pope will remain in hospital for a “few days” with a respiratory infection, the Vatican has said.
“Pope Francis is touched by the many messages received and expresses his gratitude for the closeness and prayer,” a statement said.
He has complained of breathing difficulties in recent days but tested negative for Covid-19.
The pontiff, 86, was taken to hospital on Wednesday for what was described at the time as “previously scheduled” tests – though it later emerged a television interview set for Wednesday afternoon had been cancelled at the last moment.
Earlier in the day, the pope attended his weekly general audience at the Vatican and appeared in good health.
There has been speculation about the pontiff’s health for some time, with claims last year that he was considering following his predecessor Pope Benedict XVI’s decision to stand aside in his advancing years – though he has insisted he has no plans to resign anytime soon.
Pope Francis is known to suffer from diverticulitis, a condition that can infect or inflame the colon, and had an operation at the Gemelli hospital in 2021 to remove part of his colon.
He said in January that the condition had returned and that it was causing him to put on weight, but that he was not overly concerned.
He also has a problem with his knee and alternates between using a cane and a wheelchair in his public appearances.
Last July, returning from a trip to Canada, the pontiff acknowledged that his advancing age and his difficulty walking might have ushered in a new, slower phase of his papacy.