The State Department said Monday that at least nine American citizens have been killed in the weekend Hamas attacks on Israel, raising the toll from four.

It says an undetermined number of American citizens remain missing and unaccounted for.

On Sunday, an official said that number was fluid and had ranged from between six to 12. It is not clear whether the missing had been taken hostage, were killed or are in hiding.

The State Department is in touch with families “and providing all appropriate consular assistance,” said spokesman Matthew Miller.