New York (CNN) -- Two men were arrested Friday by the FBI's Joint Terrorism Task Force in connection with the case of Najibullah Zazi, accused of conspiring to use weapons of mass destruction on U.S. soil.

The FBI identified them as Adis Medunjanin and Zarein Ahmedzay.

Authorities had seized the passport Thursday of Medunjanin, 25, a Bosnian immigrant who was previously questioned in connection with the case against Zazi.

Authorities say Zazi, 24, who has pleaded not guilty to conspiracy charges, planned to be in New York and use an explosive device on September 11, 2009.

Medunjanin voluntarily turned over the passport when the FBI showed up, said his attorney, Robert Gottlieb.

"We were looking for his passport, and we got it," FBI spokesman Rich Kolko said.

"We have no idea why they wanted his passport," Gottlieb said. The FBI did not explain.

Medunjanin arrived in the United States in 1994 and was naturalized in 2002.

His home in the Whitestone neighborhood of the New York borough of Queens was searched in September when the Zazi investigation broke. Medunjanin, his sister and parents were interviewed at the time as part of the investigation, Gottlieb said. Medunjanin talked with police for about 14 hours at that time, he said.

Medunjanin has denied any knowledge of the case.

Ahmedzay, a taxi driver who also has an address in Queens, had also been questioned in the case.