By Steve Gorman

LOS ANGELES (Reuters) - Actress Lindsay Lohan was arrested in the Los Angeles area early on Tuesday on suspicion of drunken driving and cocaine possession, just days after she completed a 45-day rehabilitation program, authorities said.

The 21-year-old star of "Mean Girls" -- already facing a drunken-driving charge following a car crash in Beverly Hills two months ago -- was taken into custody in the coastal city of Santa Monica shortly at about 1:30 a.m.

She was released from jail after posting $25,000 bond, and Lohan's lawyer issued a statement hours later saying the actress had suffered a relapse and that she was "presently receiving medical care."

Police said they encountered the actress in a parking lot after the mother of Lohan's personal assistant called them on her cell phone to report that she was being pursued by Lohan in an automobile chase.

Police Lt. Alex Padilla told a news conference that the personal assistant had just quit her job hours earlier.

"(Lohan) was trying to catch the mother of her personal assistant. Why she was trying to catch her, we don't know," Padilla said. "The mother was afraid ... She wasn't quite sure what was going on, so she called the police because she wanted to make sure everything would be OK."

Padilla said Lohan was accompanied in her sports utility vehicle by two friends, who were questioned and released.

Lohan was detained after failing a field sobriety test. Police said she was later tested and registered a blood-alcohol level of about 0.12 percent, well above the California limit of 0.08.

LOHAN'S TROUBLES

Lohan was booked on suspicion of drunken driving, possession of cocaine, bringing a controlled substance into custody and driving on a suspended license. Padilla said a small amount of cocaine was found in her possession while she was in jail.

Just last Friday, Lohan turned herself in to Beverly Hills police to face charges of drunken driving in connection with a May 26 car crash.

In that case, she lost control of her Mercedes-Benz sports car and drove into a hedge. She then left the scene. Police said at the time they also found a small amount of what they believed to be cocaine in the car.

The incident followed months of hard partying by the actress, who had been a regular at Hollywood nightspots and had attended Alcoholics Anonymous programs for a year despite having turned 21 -- the legal age for drinking in the United States -- only this month.

Immediately after the crash in May, Lohan checked herself into a Malibu rehab center for the second time in a year. She left earlier this month and was wearing an alcohol-monitoring bracelet on a voluntary basis, her spokeswoman said.

"Addiction is a terrible and vicious disease," her attorney, Blair Berk, said in a statement after Tuesday's arrest, adding that Lohan had been undergoing daily testing "to support her sobriety."

"Unfortunately, late yesterday, I was informed that Lindsay had relapsed," Berk said. "The bracelet has now been removed. She is safe, out of custody and presently receiving medical care."