Some 50,000 people have flooded the basilica to pay homage to the late pontiff since his body was laid out on Wednesday in an open coffin ahead of his funeral on Saturday, Vatican officials said.
Francis died aged 88 on Monday morning in his rooms at the Vatican's Santa Marta guesthouse, having only recently left hospital after five weeks being treated for double pneumonia.
"He was a wonderful pope," said Rome resident Alessandra Caccamo, as she queued outside the Vatican.
"I'm going to miss him so much, because it's like I've lost a piece of me."
The basilica had been initially scheduled to close at midnight on Wednesday but given the size of the crowds, officials kept it open until 5.30am before it reopened at 7am.
The head of the pontiff's medical team said in interviews published on Thursday that Francis had died quickly from an unexpected stroke without suffering undue pain.
"I entered his rooms and he (Francis) had his eyes open," Sergio Alfieri told Corriere della Sera newspaper.
"I ascertained that there were no respiratory problems. And then I tried to call his name, but he did not respond to me.
"In that moment I knew there was nothing more to do."
Francis, who was from Argentina and was the first non-European pope in 1300 years, had an often turbulent 12-year reign in which he repeatedly clashed with church traditionalists and championed the poor and marginalised.
On Saturday, more than 170 delegations including heads of state and government including US President Donald Trump are expected in St Peter's Square for the funeral ceremony, with millions more watching on television across the globe.
"A chapter in the Church's history has been closed," Cardinal Gerhard Ludwig Mueller told Italian daily La Repubblica in an interview published on Thursday.
Mueller is one of the 135 cardinals eligible to vote in the secret conclave that will be held next month to elect the church's 267th pontiff.
The German cardinal said that there was "unanimous appreciation" for the late Pope's work on migrants and the poor.
However he said that the task was to choose a successor to St Peter, the first pope, rather than Francis, indicating he favoured a change of direction.
18°C