Transit officials say anti-Semitic graffiti incidents are the top subway bias crime investigated so far this year by the New York Police Department.

The Daily News reports that the Metropolitan Transportation Authority’s Transit Bureau says 22 of 31 hate crimes that have happened in the subway system this year targeted Jews. Most of the incidents involved graffiti.

The report to the MTA board says there were only seven bias crimes committed during the same period last year.

Transit police say each case gets an investigation from a captain or a higher ranking officer, but it’s sometimes difficult to make arrests. The anti-Semitic graffiti on subway cars and in stations has included swastikas and comments that advocate the killing of Jews.

Officials say felony assault cases and grand larcenies have also increased this year.

(AP)