Federal investigators confirmed the car contained Arabic-language flight training manuals, and The Boston Globe reported that authorities also found two bags belonging to one of the suspect’s—containing an instructional video on flying commercial airliners, a fuel consumption calculator and a copy of the Koran—that did not make a connecting flight.

In addition, outside Boston, police officers converged on the Park Inn at Chestnut Hill in Newton. Newton police officer Russ Adam said the FBI was conducting an investigation at the hotel, but declined further comment, although news agencies reported that agents found airline paraphernalia and flight-related material at the location.

Juliette N. Kayyem, executive director of the Kennedy School’s domestic preparedness program, said that several factors could have attracted the terrorists to the Boston area.

“Our proximity to the Canadian border and Boston being a big city where people can hide is likely why Boston became the center,” Kayyem said.

Scare In Back Bay

A heavily armed team of FBI agents and Boston police converged on a posh Back Bay hotel yesterday afternoon after an anonymous tip pointed them to suspects on the 16th floor.

The FBI detained three people at the Copley Westin Hotel shortly after noon yesterday, although all had been released by last evening.

At about 12:30 p.m., a heavily armed SWAT team clad in bulletproof gear and helmets entered the building with shields, special entry gear, a battering ram and fiber-optic equipment, which the police used to peak under doors in the hotel. The Boston Police Bomb Squad arrived shortly after 1 p.m., and four Boston ambulances waited outside with lights flashing, including a special tactical response unit with EMTs in bulletproof vests and helmets.