At first, officials said they believed that the sensors had been set off by criminals at the border.
It was the first time in several years that a car bomb had been set off in the city.
The protests had been set off by the death of the reform-minded party leader Hu Yaobang.
An employee at the club said the canisters had been set off inside the club, not thrown in from outside.
Spanish investigators said they believed the bombs had been set off by cellphones, not suicide bombers, Mr. Kelly said.
The police chief said that three "explosive devices" had been set off by individuals in the crowd.
Eight years of deadly civil war had been set off by the army interrupting an election to prevent an Islamist party from winning.
The chief executive said that the breakdown on Thursday had been set off by another participant in the market, not something within Nasdaq's control.
Although the hotel is next to the city's fireworks celebrations, no fireworks had been set off at the time of the fire.
An Iraqi police chief said the perpetrators were mentally retarded and that their explosives had been set off by remote control.
News reports said the bomb had been planted in trees nearby; some reports said it had been set off by a timer.
