Police said a small bag of cocaine, 0.8 grams, later fell out of the socialite's purse, but Hilton said the drugs were not hers.
"She told me the purse was not hers and that she had borrowed it from a friend," Las Vegas Police Lt. Dennis Flynn wrote in his report. "I asked Hilton whose cocaine it was, and she said she had not seen it but now thought it was gum."
Hilton told police the purse belonged to a friend, but the friend was never identified.
Police said Hilton did acknowledge owning $1,300 in cash, several credit cards, prescription asthma medication and a package of rolling papers found inside the purse.
West coast editor of Parade Magazine, Jeanne Wolf, said Hilton's stories may be wearing thin.
"If you watch cop shows, whether they're so-called reality shows or dramas, isn't the bad guy always dropping bundles of drugs and guns and saying 'It's not mine'?" Wolf said. "Paris has just picked up a very corny line."
Hilton is no stranger to the legal system. The celebutante has spent 23 days in jail stemming from DUIs.
The 30-year-old is scheduled for arraignment before a Las Vegas judge Oct. 27 on a felony cocaine possession charge that could get her probation if convicted.
This is the third time this year that she's been accused of drug possession. Hilton was detained last month by authorities on a French island after allegedly being caught with less than one ounce of marijuana in her bag. She was arrested in South Africa during the World Cup on marijuana charges, but the charges were dropped.
"I think Paris has created a nationwide rolling of the eyes," Wolf said. "If you took a poll, I can't imagine anyone who believes her at this point."
Hilton was freed without bail after spending less than three hours handcuffed on a booking room bench at the Clark County jail.
Her 34-year-old boyfriend spent the night in jail and was released on $2,000 bail. He faces a charge of DUI.
On her Twitter account, Hilton wrote, "I'm so thankful to all my fans for all the love and support you are giving me. Thank you all. Love you so much. Love Paris XOXO."
Hilton's lawyer, David Chesnoff, said he would not comment on the police report, and added, "the facts of the situation will be tested in a courtroom."
The Associated Press contributed to this report.