Additional refund/ Reason unknown

On May 19, I received my IRS refund ($2,605.99) which went via direct deposit into my US bank account. This was $5.99 more than I had expected. One week later, I received another (!!) IRS deposit into the same bank account for a different sum ($2,800). There is a trace# for both deposits. I submitted my federal tax via Turbo Tax for free. I live abroad. I never got contacted by the IRS, but this must be in error. Any advice?