MIAMI – Seven people were arrested Thursday in connection with the early stages of a plot to attack Chicago’s Sears Tower and other buildings in the U.S., including the FBI office in Miami, a federal law enforcement official said.

As part of the raids related to the arrests, FBI agents swarmed a warehouse in Miami’s Liberty City area, using a blowtorch to take off a metal door. One neighbor said the suspects had been sleeping in the warehouse while running what seemed to be a “military boot camp.”

The official said the alleged plotters were mainly Americans with no apparent ties to al-Qaida or other foreign terrorist organizations. He spoke on condition of anonymity so as not to pre-empt news conferences planned for today in Washington and Miami.

“There is no imminent threat to Miami or any other area because of these operations,” said Richard Kolko, spokesman for FBI headquarters in Washington.

Residents living near the warehouse said the men taken into custody described themselves as Muslims and had tried to recruit young people to join their apparently militaristic group.

The residents said FBI agents spent several hours in the neighborhood showing photos of the suspects and seeking information. They said the men, who appeared to be in their teens or 20s, had lived in the area about a year.

The men slept in the warehouse, said Tashawn Rose, 29. “They would come out late at night and exercise. It seemed like a military boot camp that they were working on there. They would come out and stand guard.”

She talked to one of the men about a month ago: “They seemed brainwashed. They said they had given their lives to Allah.”

Rose said the men tried to recruit her younger brother and nephew for a karate class. “It was weird,” she said.

Benjamin Williams, 17, said the group had young children with them sometimes. Sometimes, he added, the men “would cover their faces. Sometimes they would wear things on their heads, like turbans.”

Xavier Smith, who attends the nearby United Christian Outreach, said the men would often come by the church and ask for water.

The 110-floor Sears Tower is the nation’s tallest building. Security was ramped up after the Sept. 11 attacks, and the 103rd-floor skydeck was closed for about a month and a half.

The FBI’s headquarters in Miami sits near a residential neighborhood just east of Interstate 95.

A huge crowd – up to 250,000 people – was expected downtown Friday for a parade to honor the NBA champion Miami Heat. Security measures consistent with such an event were in place, city officials said, and the raids were not expected to affect it.