Selena Gomez has been to the hospital twice since being taken ill after taping The Tonight Show with Jay Leno on Thursday, June 9; according to reports, the teen star is being investigated for high blood pressure.
Sources tell TMZ that "Gomez has undergone a number of tests for blood pressure issues, but so far ... doctors have not been able to determine what is causing the problem."
Selena, 18, was rushed to a LA area hospital after she complained of severe headache and nausea Thursday night.
She returned to hospital on Saturday, June 11 for a medical checkup.
Her rep said in a statement that she was undergoing routine tests.
Earlier today Us magazine quoting an insider reported that "Selena collapsed from food poisoning coupled with exhaustion."
FOX confirmed to Access Hollywood on Saturday that Selena's sold out Sunday appearance at Santa Monica Place Center Plaza has been rescheduled to Monday, June 13.