美國聯邦調查局對波士頓馬拉松致命的爆炸案展開調查

U.S. federal investigators are working to uncover who was behind a twin bombing Monday at the Boston Marathon that left at least three people dead and more than 140 others injured.

The Federal Bureau of Investigation is leading the multi-agency effort to investigate what a White House official said was "clearly an act of terror."

The FBI said in a statement late Monday it was too early to establish the cause or motivation for the explosions, which happened moments apart within about 100 meters of each other near the finish line.

VOA correspondent Carolyn Presutti said early Tuesday investigators were working in a wide area around the scene, with barricades on street corners to keep out people and traffic.

She described a lot of security around the city with the sights and sounds of police cars and sirens, but otherwise no one out on the streets.

U.S. President Barack Obama said in televised remarks that the United States will find out who was responsible for the blasts and hold them accountable.

Boston Police Commissioner Edward Davis said there was "no specific intelligence" warning of an attack, and authorities said there was no immediate claim of responsibility.

The blasts took place about four hours into the race, long after the winners had finished, but at the time that the highest number of runners and their supporters are usually around the finish line area. The competition, which had more than 23,000 runners, was halted after the bombs went off.

Bloody spectators, including some with severed limbs, were carried to the medical tent that had been set up to care for fatigued runners from the race.

The Boston Globe, citing two law enforcement sources, reported that the dead included an eight-year-old boy. A number of victims suffered amputations.

Cities worldwide stepped up security following the explosions.美國聯邦調查局開始尋找星期一波士頓馬拉松賽連環爆炸案的製造者，這一事件造成至少三人死亡，140多人受傷。

聯邦調查局正在組織多個機構對爆炸事件展開調查。一名白宮官員說，這一事件“顯然是恐怖活動”。

聯邦調查局星期一晚間發表聲明說，現在確定這次爆炸事件的起因或動機還爲時過早。這兩次爆炸都發生在馬拉松賽終點線附近，爆炸地點相距大約在百米之內，間隔時間極短。

美國之音記者普雷蘇蒂星期二清晨說，調查人員在爆炸現場周邊很大範圍內展開工作，街角設有路障，不準行人車輛進入。

普雷蘇蒂說，波士頓加緊保安工作，可以看到警車，並能聽到警報器的聲響，但街上沒有行人。

美國總統奧巴馬在電視講話中說，將找到肇事者，並將其繩之以法。

波士頓警方首腦戴維斯說，沒有關於這次襲擊的情報。有關當局表示，目前還沒有人宣稱對爆炸事件負責。

爆炸發生在馬拉松賽開始大約四小時後，一些選手早已跑過終點，而當時大量選手及其支持者聚集在終點線周邊。比賽在爆炸發生後停止，參賽選手有2萬3千多名。

鮮血淋漓的觀衆，包括一些被炸斷手臂或腿的人，被送到原本爲疲憊的長跑運動員設置的醫療帳篷內。

波士頓環球報援引兩名執法機構消息人士的話說，死者中包括一名八歲男孩。一些人的手臂或腿被炸斷。

爆炸發生之後，全球各地的城市已經加強了保安的措施。