Amy Winehouse remains in hospital in London after fainting at home on Monday afternoon, with tests on the singer so far proving "inconclusive".
"She seems to be fine in herself, but they are taking their time
to be sure," her spokesman said.
Winehouse had been "doing admin" when she fell ill but "quickly recovered".
Her manager's assistant had stopped her falling and Ms Winehouse's father, Mitch, had taken her to hospital "as a precaution", the spokesman added.
After receiving treatment, she stayed at the London Clinic for observation.
The 24-year-old had been signing autographs for Canadian fans who had been waiting outside her house all day, her spokesman said.
There have long been concerns about Winehouse's health.
Last year, she was admitted to a hospital in London suffering from "severe exhaustion", and there were reports she was being treated in a rehabilitation clinic.
And following a succession of cancelled gigs, the singer's father spoke out about her drug use.
Mitch Winehouse told BBC Radio 5 Live his daughter and her husband Blake Fielder-Civil had "serious problems" but said neither was in "imminent danger of death".
Police confirmed in May that Winehouse would not face charges over a video that purported to show her smoking a crack cocaine pipe.
Earlier this year the singer was cautioned by police after admitting a common assault following an incident in Camden, north London.
Last week it was confirmed Winehouse had played an exclusive concert at an art gallery in Moscow for Chelsea FC owner Roman Abramovich.
And later this month she is due to be on the bill in London's Hyde Park, at a gig marking the 90th birthday of former South African president Nelson Mandela.
The singer's hits include Rehab - including the refrain "they tried to make me go to rehab/ I said no, no, no" - and Back to Black, the title track from her current album.