Investigators found research on New York City sports stadiums and sites related to the city's Fashion Week events on the computer of a man being questioned in an FBI probe of an alleged terrorist plot, ABC News reports.

Authorities have made few public comments about the progress of their investigation, but there have been numerous reports that Najibullah Zazi has admitted to ties to Al Qaeda while claiming he was not central to the suspected terror cell under investigation.

Zazi had been cooperating with authorities and was interviewed several time this week by investigators, but on Saturday, he apparently didn't report for a fourth day of FBI questioning. His attorney has said the reports of a confession to terror ties were untrue.

The FBI had no immediate comment.

Zazi, a 24-year-old airport shuttle driver, insists he is not involved in terrorism and has no links to Al Qaeda. He is not under arrest.

U.S. Attorney General Eric Holder said Friday that the FBI was "working this case around the clock" in New York, Denver and other parts of the country but that there was no imminent threat.

Authorities say Zazi rented a car and drove from Denver to New York, crossing into Manhattan on Sept. 10. Zazi said he went to New York to resolve some issues with a coffee cart he owns in Manhattan.

On Monday, FBI agents and police officers with search warrants seeking bomb materials searched three apartments and questioned residents in the Queens neighborhood where Zazi stayed.

ABC News reports officials said they aren't sure what locations might have been targeted, but infomation found on Zazi's computer may provide a window into what he might have been planning. They reporteldy also found a text message that said "wedding cake is ready," which may have been a signal about preparations for an attack.

A joint FBI-New York Police Department task force feared Zazi may have been involved in a potential plot involving hydrogen peroxide-based explosives like those cited in an intelligence warning issued Monday, according to two other law enforcement officials, who spoke to the Associated Press on condition of anonymity because they were not authorized to speak about the investigation.

Zazi's attorney, Arthur Folsom, has repeatedly denied any such claims.

Zazi's defense team has denied reports that Zazi was considering a plea deal related to terror charges.

"At this time no offer is being discussed," Wendy Aiello, spokeswoman for the defense team, told The Associated Press late Friday.

Another official familiar with the investigation told the AP on Thursday that agents have been monitoring Zazi and four others in Colorado as part of a terrorism investigation.

Zazi was born in Afghanistan in 1985, moved to Pakistan at age 7 and emigrated to the United States in 1999. He returned to Pakistan in 2007 and 2008 to visit his wife, Folsom said.