Emergency services were called to a hotel in Riviera Beach, Florida, according to US celebrity website TMZ.

Her father told the website that Capriati, 34, was "recovering well" in hospital.

Capriati burst onto the tennis scene as a teenager reaching the semi-finals of Wimbledon in 1991 at the age of 15 after defeating then defending champion Martina Navratilova.

But her early career was blighted by personal problems incuding a shoplifiting incident in 1993 and an arrest for possession of marijuana the following year. She did not play at all in 1995.

She later mounted a successful comeback and won three Grand Slam singles titles – the Australian Open in 2001 and 2002, and the French Open in 2001.

In recent years she has suffered from a persistent shoulder injury and admitted to feeling depressed and having suicidal thoughts in a 2007 interview.

"It's like you're being taken over by a demon," she told the New York Daily News. "You just feel there's no way out of this space you're in. It feels like the end of the world.

"When you are just so exhausted and tired of feeling that way you think 'I want to be off this planet right now, because I just feel disgusting inside.

I can't even stand my own skin, and I just want to get out.'"

A spokesman for Capriati later said she had suffered an “accidental overdose” of prescription medication.

She said: “Jen is recovering fully and speedily.”

Capriati remains unmarried but has in the past dated Friends actor Matthew Perry and Belgian tennis player Xavier Malisse.

Neighbours at her apartment building saw ambulance crews going in with oxygen equipment. She spends weekends at the 19th floor $1.6 million (£1 million) property.