New Jersey health officials issued a warning about a potential measles exposure during the Shakira concert at MetLife Stadium.

According to the New Jersey Department of Health, concertgoers at a recent Shakira concert held in MetLife Stadium may have been exposed to measles. This comes after the recent discovery that a fan from outside the state attended the concert while infected with the disease on May 15.

Shakira fans who attended the singer’s Thursday show at MetLife Stadium are being warned by health officials that at least one concertgoer had the measles.