Spanish police are investigating whether Cilla Black's death was caused by a fall from a dizzy spell, caused by a sudden temperature change in the room.
Black may have walked from an air-conditioned room in to midday heat, with the change in temperature causing her to become dizzy, the Sun newspaper reported.
A post-mortem examination is due to be carried out today, to determine the cause of death, but police in Spain have said "everything at this stage is pointing towards her death being the result of natural causes".
Her sudden death at her home in the south of Spain has left friends, family and the British public in shock.
Tributes have been pouring in for Black, 72, led by close friends such as Sir Cliff Richard, Sir Paul McCartney and Christopher Biggins.
She rose to fame in the 1960s as an associate of The Beatles and their manager Brian Epstein.
Born Priscilla Maria Veronica White in Liverpool, she became the first woman to have her own prime-time chat show on BBC1.
Her star continued to shine brightly, and she had two number ones in 1964 - Anyone Who Had A Heart and You're My World.
Tributes to entertainment icon
In a touching tribute to her, Sir Cliff Richard said he was due to visit her at her house in Spain next week.
"Her passing away is a particular shock because despite the aches and pains we all suffer, she was always so upbeat," he wrote in the Sun.
Former Beatle Sir Paul McCartney paid tribute to her from Los Angeles, saying: "Such a shock to hear about Cilla's passing. She was a lovely girl who infected everyone with her great spirit.
"From first meeting her as a cloakroom girl at the Cavern in Liverpool, to seeing her many times since, she always had a fun-loving dignity that made her a great pleasure to be around.
"She had a fine distinctive voice and was always a bit of a laugh. It was a privilege to know and love her."
And former Beatles drummer Ringo Starr said: "I just heard the news Cilla Black has left us. She was a good friend, we will all miss her. Peace to Cilla, peace and love to the family, R&B."
EastEnders star and her good friend, Barbara Windsor, described her death as "awful".
She told the BBC: "I was only with her a couple of weeks ago. I've seen her twice in the last few weeks, and as always she looked immaculate. That was the thing about Cilla, she always looked spot-on. But I knew she wasn't very well, she didn't seem well."
Windsor added: "I liked her, we got on well. She was nothing like me in personality at all, but she was a good, good all-round performer."