On Monday, the New York Police Department sent its warrant squads after an unusual set of suspects: people who had old warrants for the lowliest of violations, misconduct too minor, usually, to draw the attention of those squads.

But those who were questioned by the warrant squads said the officers had an ulterior motive: gathering intelligence on the Occupy Wall Street protests scheduled for May 1, or May Day. One person said he was interviewed about his plans for May Day. A second person said the police examined political fliers in his apartment, and then arrested him on a warrant for a 2007 open-container-of-alcohol violation.

Officials have yet to respond to questions about the tactics, but one police official, who spoke on condition of anonymity because he was not authorized to speak to reporters about police policy, said the strategy appeared to be an extension of a policy used at events where crowd control could be an issue. Before certain parades that have been marred by shootings, for example, the warrant squads have tracked down gang members who live nearby to execute outstanding warrants, no matter how minor, the official said.

But the department’s use of this tactic as part of its strategy for policing the Occupy Wall Street movement raises new questions about the surveillance efforts by the Police Department, which faces restrictions in monitoring political groups.

Zachary Dempster, 31, said he was wakened at 6:15 a.m. Monday by plainclothes police officers who entered his apartment on Myrtle Avenue in Brooklyn and herded him and two roommates into the living room. There, Mr. Dempster said, the police announced they were there that morning to serve an open-container warrant on one of the roommates, Joseph Ryan, a musician who goes by the name Joe Crow Ryan. But then one of the officers led Mr. Dempster back to his room for questioning.

“The officer said, ‘What are you doing tomorrow?’ ” Mr. Dempster recalled. “Do you have plans for May Day?”

“I said, ‘I’m not going to talk to you without my lawyer present,’ ” Mr. Dempster said, adding, “It didn’t seem right.”

Mr. Dempster had been arrested on an assault charge in January during a fracas at an “Occu-Party” that the police broke up in Williamsburg, Brooklyn. He speculated that the police probably associated him with the Occupy movement, based upon that arrest.

But Mr. Dempster said that he was not particularly involved, beyond visiting Zuccotti Park, the protesters’ main encampment, in the fall. He noted, “I haven’t even Facebook-liked Occupy Wall Street.”

“Possibly they were casting a net to see what they could pull in,” Mr. Dempster said about the visit to his home on Monday.

Although Mr. Dempster was not arrested, he said the police arrested Mr. Ryan.

It is unclear exactly how many times the police inquired about May Day activities during warrant checks on Monday.

Gideon Oliver, a lawyer who has represented Occupy Wall Street protesters, said he heard of five addresses where the police had shown up in the last week to inquire about May Day activities and event organizers.

Mr. Oliver said that he believed the visits, reported on Monday by the Web site Gawker, were intended to discourage people from “engaging in First Amendment activity on May Day.”

“I was surprised by the fact that bench warrants would be used as a pretext to this kind of activity as opposed to the officers knocking on the door and saying we want to talk to X, Y and Z,” Mr. Oliver said.

Paul J. Browne, a Police Department spokesman, did not respond to repeated calls over the last two days seeking comment.

About an hour after the police visited Mr. Dempster’s home, a warrant squad stopped by another home in Brooklyn, again to serve an open-container complaint. “I woke up in bed to a rather large detective standing over me with a flashlight,” said Sean Broesler, a resident of the home. He said that he and his roommates were brought into a common area.

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