NEW YORK (CBSNewYork) — A bomb threat prompted Mercy College to evacuate and close its campus in Midtown Wednesday afternoon.

The Mercy College Manhattan Campus, at 66 W. 35th St. at Herald Square was closed until further notice as of 6 p.m. and all evening classes were canceled.

Police said a letter was dropped off at the security desk claiming that there were two bombs in the college building and that they would go off 30 minutes apart.

The letter said the reason for the bombs was because of how poorly the college was treating minorities, police said.

Mercy College occupies the sixth and seventh floors of the 35th Street building. Both floors were cleared after evacuation, and no bombs were found, police said.

The investigation was ongoing late Wednesday and there had been no arrests.

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