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Selena Gomez is undergoing tests at a Los Angeles-area hospital after being rushed there Thursday night, shortly after appearing on Jay Leno's "The Tonight Show."

Selena's rep told People magazine in a statement:

"Last night after Selena's appearance on The Tonight Show, she wasn't feeling well and was taken to the hospital. She is currently undergoing routine tests."

Sources tell TMZ that Selena had a bad headache and nausea while on the show and after it.

Selena, 18, appeared on Jay Leno to plug her upcoming film Monte Carlo and seemed in good cheer as she talked about getting a driver's license and her beau Justin Bieber's recent meeting her mother.

As to 17-year-old Bieber's meeting with her mother, Selena said, "He passed the test."

The 18-year-old star has canceled her Friday night appearance at Santa Monica Place to promote Monte Carlo.

This morning Bieber showed support for his girlfriend on Twitter with an uncharacteristically short tweet, "#getwellselena."

Co-incidentally, Jennifer Hudson was also hospitalized with food poisoning Friday morning after performing on "Good Morning America," after she complained of severe stomach pain. She has since been released.

Hudson's rep told TMZ, "After performing on 'Good Morning America' earlier today, Jennifer Hudson went to the hospital due to severe abdominal pains."

"She was treated for food poisoning and released," the rep added.