SANTA MONICA, Calif. -- Pop superstar Michael Jackson was released from the hospital Thursday night after a four-day stay for chest pains, a spokeswoman said.
The Grammy-winning singer was released a day after doctors announced he was suffering from an extremely painful inflammation in his ribs, thought to be caused by over-exertion or stress.
'At 9 p.m., he went home and is resting comfortably in stable condition,' a spokeswoman for St. John's Hospital and Health Center said.
Jackson's release was not announced until after he left the hospital, where a number of fans had been keeping a vigil since he was admitted. He had sent them autographed pictures.
The cause of his condition was a mystery until a battery of tests revealed he was suffering from costochondritis, or a cartilage inflammation that affected the front part of his ribs, said Bob Jones, his spokesman.
Jackson checked himself into St. John's Sunday night after experiencing the chest pains during a dance-exercise session at home. He had more spells of chest pains while in the hospital.
The tests, ordered by Jackson's physician, cardiologist Mark Zatskis, revealed no physical abnormalities other than the inflammation, Jones said.
Jackson is expected to receive follow-up treatment after his release.
Jones said the inflammation can be caused by 'over-exertion and stress and is usually extremely painful,' adding the star's condition 'will absolutely not affect his career.'
The clean-living, lean pop star, who shuns alcohol, cigarettes and junk food, has no history of serious health problems. But Jones said the recent deaths of his maternal grandmother and of entertainer Sammy Davis Jr., a close friend, had put Jackson under some stress.
In addition, the excruciatingly shy star has been working on a new album, titled, 'Decade,' that is eight months overdue and now scheduled to be released in August.
Jackson was visited Wednesday by his brothers -- Jackie, Marlon and Randy -- and his sister Rebbie, who briefly greeted fans outside the hospital.
During his stay, Jackson had visited his friend, actress Elizabeth Taylor, who has been recovering at St. John's from a near-fatal bout with pneumonia since mid-April.
Jackson ventured from his singing brothers, the Jackson 5, with the Grammy-winning solo album 'Off the Wall' in 1980. He has recorded only two albums in the past seven years -- 'Thriller' in 1983 and 'Bad' in 1987. The albums sold a combined 60 million-plus copies, earning him an estimated $100 million.
When sales of 'Thriller' hit the 24 million mark, the Guinness Book of World Records halted printing of its 1984 edition to include Jackson as history's best-selling solo performer. Seven Top 10 hits emerged from the LP.