Britney Spears left rehab on February 21 – the second time in two weeks that she had fled a treatment facility. The pop star’s weird public behavior has former friends and acquaintances worrying that she is out of control and using drugs-something that they say has been going on for years.

In the March 5 issue of In Touch, several people who know Britney came forward to reveal that her drug use began many years ago. “When I was around her, she took Ecstasy,” Amanda Alexander, the sister of Britney’s first husband, Jason, tells In Touch. Amanda says she also witnessed the singer using cocaine in their hometown of Kentwood, La.

Another hometown friend, Kent Smith, who’s known Britney for “at least 10 years,” says he partied with her three years ago at Club 360 in New Orleans. “She does like to party,” Kent tells In Touch. “I’ve been there when she’s done Ecstasy and cocaine.” ‘\

Toward the end of her marriage to Kevin, insiders say Britney returned to drug use. According to a pal, the couple got into a huge fight about it on the night of his CD release party last Halloween. “Kevin was mad because he knew she was high on coke,” says an insider.