Police said the 26-year-old singer was arrested early Saturday morning after they saw a dark sport utility vehicle drive into the parking lot of a restaurant that had been closed for more than an hour.
DeMato, who made the top 10 in season two of "American Idol," failed field sobriety tests, police said. They said a search of her SUV found two marijuana pipes, a small quantity of marijuana and a baggie with a small amount of white powder that tested positive for cocaine.
She told the News-Times of Danbury that it was just a misunderstanding.
"I am not a drug user," she told the newspaper in a phone interview from her home. "It's going to be taken care of in court and that's that."
DeMato, who was released on $10,000 bond, is due in court on Dec. 16.
"American Idol" airs on FOX, which is owned by News Corp., the parent company of FOXNews.com