Madonna was "strenuously rehearsing" 12 hours a day before she was hospitalised with a "serious bacterial infection".

A source said the Queen of Pop, 64, who is recovering after being rushed to an intensive care unit with the illness, was putting in epic hours in preparation for her upcoming 'Celebration Tour' at Long Island's Nassau Coliseum for weeks before she was said to have been found unresponsive and intubated by medics.

An insider told Page Six: "She had been putting in 12-hour days. She was strenuously rehearsing and putting in the work."

Madonna has now postponed her upcoming greatest hits tour, with her manager Guy Oseary, 50, taking to Instagram on Wednesday (June 28) to tell fans the stayed in an intensive care unit for several days - with reports saying she had been found unresponsive and had to be intubated by medics.

He said: "On Saturday June 24, Madonna developed a serious bacterial infection which led to a several day stay in the ICU.

"Her health is improving, however she is still under medical care."

Guy added Madonna's team expected her to make a "full recovery", but stated they were pausing "all commitments" including Madonna's much-anticipated 'Celebration' tour.

He also promised fans more information and rescheduled tour dates would follow soon, adding: "We will share more details with you as soon as we have them, including a new start date for the tour and for rescheduled shows."

Madonna was treated at a New York City hospital on Saturday (June 24), according to Page Six.

The outlet said a source told them the 'Material Girl' singer was intubated for at least one night before having the tube removed, but is now "alert and recovering".

It added: "We're also told that her daughter Lourdes Leon was by her side throughout the ordeal."

Madonna announced earlier this year she would launch her 'Celebration' tour in honour of the 40th anniversary of her music career.

Her 84-date global shows were due to kick off on 15 July at Rogers Arena in Vancouver, and she has been regularly updating fans by sharing images and videos from her rehearsals online.

In one of her latest recent set of snaps on Instagram showing her preparing for the 'Celebration' gigs, mum-of-six Madonna said: "Calm before the storm… ."

The singer - who first entered the US Billboard Hot 100 with 1983's 'Holiday' - last July said about how she was keen to get back on stage: "I want to go on tour again. I'm a creature of the stage. That's my happy place."

Source: Bang