Police checked websites run by Muslim student groups at 16 colleges in the Northeast, including Yale. They talked with local authorities about professors in Buffalo and even sent an undercover agent on a whitewater rafting trip. The agent recorded students' names and noted how many times they prayed.
NYPD spokesman Paul Browne says arrests or convictions of former members of Muslim student associations made it "prudent to get a better handle on what was occurring at MSAs."
Critics see a violation of human rights and say that Muslim students just want the same freedoms everyone else has.
The NYPD says it follows the same rules as the FBI but some activities go beyond what the FBI is allowed to do.