A family in northern Mexico says their son who needs a heart and liver transplant has been denied a U.S. visa to go to the Mayo Clinic for treatment.

Myra Lopez Martinez says her son, 20-year-old Jose Chua Lopez, was born with a heart defect and could die if he doesn't receive the transplants.

She says he has an appointment at the Mayo Clinic in Rochester, Minnesota, in 10 days, but was turned down for a visa Tuesday by the U.S. State Department for the second time.

The State Department says it can't comment on visa applications because they are confidential.

State Department spokeswoman Jen Psaki says that "our team is looking into it. So we'll see if there's more information they can provide."