Hotel heiress Paris Hilton faces cocaine possession charges after being arrested on the Las Vegas Strip at the start of the weekend.

Las Vegas police say they stopped a black Cadillac Escalade late Friday night after officers believed that marijuana smoke was wafting out of it.

"Officers noticed a vehicle leaving smoke trail of a controlled substance (and) made a stop based on that," police spokesperson Marcus Martin told The Associated Press.

Martin said officers found that Hilton -- who was a passenger in the vehicle -- was in possession of something that appeared to be a drug, which tests later confirmed to be cocaine. He did not say how much of the drug was found.

The 29-year-old socialite was booked into the Clark County Detention Center in the early hours of Saturday morning. But she was later released on her own recognizance.

Police watch commander Lt. Wayne Holman confirmed Hilton's release, but did not have details on a possible court date. He also did not know how long she was held in custody.

Holman said the man driving the vehicle was arrested on charges of driving under the influence of alcohol or drugs. Police later said that the driver of the vehicle was Cy Waits, a 34-year-old man whom The Associated Press identified as a Las Vegas nightclub mogul and Hilton's boyfriend.

Later Saturday, Hilton's attorney, David Chesnoff, urged people "not to rush to judgment."

Chesnoff told The Associated Press that he was still gathering information on Hilton's arrest.

Hilton has yet to comment on her arrest, though it appeared that she was updating her Twitter account in recent hours. After her arrest, she let her online followers know what she was watching on TV and when she was going to bed. It was unclear if Hilton posted the messages herself, or if someone else had done so.

The Associated Press reported that her manager did not immediately respond to a request for comment on Saturday, and her publicist, Dawn Miller, did not immediately reply to an email.

A week ago, police arrested a 31-year-old man who allegedly tried to break into Hilton's Los Angeles home. She posted a picture of the man's arrest on Twitter and described it as "scary."

Earlier in the summer, Hilton was arrested in South Africa on suspicion of possession of marijuana. But the case was quickly dropped.

Three years ago, Hilton pleaded no contest to alcohol-related reckless driving, for which she received a 45-day jail sentence.

With files from The Associated Press