(CNN) -- Paris Hilton was refused entry to Japan on Wednesday because of a drug conviction, immigration officials said.
The American celebrity socialite was expected to head back to the United States late Wednesday afternoon.
She had arrived in Japan on Tuesday and had been allowed to spend the night, to see whether immigration officials would reconsider their initial refusal to allow her entry. They stuck by their decision Wednesday, based on her having pleaded guilty to a drug charge earlier in the week in Las Vegas, Nevada.
Japan generally denies entry to foreigners who are on probation.
Hilton had traveled to Japan because of "business obligations planned many months earlier," her spokesman said.
"Paris was contractually bound to her business trip and didn't want to let down her brands and many Asian fans," the spokesman said.
Hilton entered guilty pleas to misdemeanor charges of drug possession and obstruction of an officer, but a felony cocaine possession charge was dropped on Monday. She was sentenced to a year on probation, a $2,000 fine and 200 hours of community service.
She was arrested on the Las Vegas Strip last month after she and her boyfriend were stopped by a motorcycle officer who smelled marijuana coming from their vehicle.
Hilton admitted in court Tuesday that a small amount of cocaine found in her pocketbook was hers.
CNN's Junko Ogura and Marc Balinsky contributed to this report.