The feds have stepped in to probe a Queens charity tied to state Assemblywoman Vivian Cook, The Post has learned.

The criminal investigation comes after The Post revealed that the Rockaway Boulevard Local Development Corp. spent much of the $2.5 million in Port Authority money it received to buy a derelict plot of land and to do street cleaning.

The PA immediately stopped sending the organization money after The Post report in March. The agency also launched its own probe of the group through its inspector general.

Now, the IG is working with the US Attorney’s Office in Manhattan, according to the PA.

Cook lobbied to get the PA money 10 years ago when the agency was building the $1.9 billion AirTrain linking Jamaica and Kennedy Airport.

The PA agreed to pay out $8 million to the Rockaway Boulevard group, which was founded by Cook in 1979. Although she is listed on the nonprofit’s tax filing as head of its board of directors, she denied she held that position.

Most of the money was going to improve a seven-block stretch of Rockaway Boulevard.

Cook did not return calls for comment.