"After every killing, there are no arrests," said Muzaffar Ali Changezi, a retired Hazara engineer.
"It's not surprising it would take them that long to make arrests," said Mark Seiden, a cybercrime investigator.
Searches were being made of properties across the country following the arrests, said Commander Richard Walton of the Metropolitan Police.
"I feel relieved with the arrests," said Quanisha's great-grandmother, Gladys Wright, 86, who spent Monday making funeral arrangements.
"There have been arrests," said Councilman John C. Liu, whose district includes Flushing.
A tip from fellow students led to the arrests, said a police spokesman.
They offered few details, and a spokesman for the American military, which regularly joins Iraqi forces during such arrests, said he had no information on those arrested.
Mr. Minor, whose criminal record included previous drug and robbery arrests, said nothing as he was led away from the courtroom in handcuffs.
News reports at the time of the arrests said that the alleged conspiracy in the case was not likely to produce an imminent act of terrorism.
But a person with knowledge of the arrests said that besides Ms. Brooks and her husband, they included Mark Hanna, the head of security for News International.
Mr. Issawi, who provided a dramatic account of the arrests, said that he had sought to call Mr. Maliki about the crisis.
