Tony Blair's tough disciplinary line for Labour MPs will be tested in one of the first votes in the Commons when the House returns after the summer recess on 14 October. The Labour leader is expected to order his troops to abstain in the annual vote on the defence estimates, to avoid being cast as being "weak on defence" Already one MP has said he will defy the whip. He had an operation on Saturday to remove shrapnel from his head and underwent further surgery yesterday.. Atlanta has been shaken by the bomb, but a decision was taken almost immediately to carry on with the Olympics.Brian Carr, 52, of Freethorpes, Norfolk, was named yesterday as the one Briton seriously hurt in the blast. Jamie Gorelick, Deputy Attorney General in charge of the investigation, said investigators were closely looking at the theory that an American was responsible. "That is one of the principal theories we are pursuing," she said on NBC's Meet the Press when asked if the FBI was looking for a "home-grown terrorist". She told CBS: "We have very promising leads, but we're not going to be releasing them as we go along." White House chief of staff, Leon Panetta, said the 900 FBI agents assigned to the case "have a lot of leads".The Olympic park was still closed off and surrounded by yellow police tape as forensic experts sifted for clues.

"The Europeans consistently refuse to recognise that Iran is a sponsor of international terrorism," he said. The European Union has, in turn, reacted badly to a new American law that calls for a US boycott of all foreign companies found to have business ties with Libya and Iran.But it is within America itself that investigators believe they will find the culprit for Saturday's Atlanta bomb. Criticism of Europe will top the agenda at an international terrorism summit in Paris tomorrow.Newt Gingrich, the Republican House Speaker, yesterday accused Europe of being too soft on states considered to be sponsors of terrorism by the US, such as Iran and Libya. As well as international guerrilla groups, US Investigators have said they are considering organised crime, insurance fraud, murder, and even suicide.More or less unfamiliar with terrorist threats until now, the American public has been tackling the growing sense of vulnerablity that first arose with the World Trade Center bombing in 1983, which killed six, and the Oklahoma City bombing in 1995 that left 169 dead.As pressure builds on politicians to offer new protection to the public, Washington is likely to turn its fire on its European partners to do more to combat terrorism worldwide. One source told the Associated Press news agency that the mystery "has a lot of similarities to Pan Am 103".No one has credibly claimed responsibility for the blast.

But the assumption that a bomb exploded on board the plane was strongly reinforced by the discovery of its forward section. Pan Am 103 was downed in 1988 by a bomb placed in the aircraft's front section. In Seattle, Washington, ferry services in Puget Sound were similarly suspended and two buildings were evacuated after two telephone warnings.A final determination that TWA 800 was indeed the target of a criminal conspiracy has not yet been made, and will not be, until investigators formally rule out massive mechanical failure as the cause. Adding to the tension was an unprecedented series of bomb scares occurring in different corners of the country in the few hours after the detonation of the pipe bomb in Centennial Olympic Park.Train services were disrupted for several hours down the length of the east coast after police received a bomb threat by telephone aimed at Amtrak's Union Station in Washington DC. The most likely cause was thought to be a terrorist bomb placed in the airliner's forward cargo hold. The twin disasters have cast a pall of anxiety across the whole of America, which, despite the Oklahoma bomb last year, remains unaccustomed to terrorism.

The discovery of the forward segment of the aircraft, which went down south of Long Island with 230 on board, suggests that it was severed from the rest of the aircraft by a violent explosion. Investigators into the crash of TWA 800 said they had found the front section of the aircraft on the ocean floor a full mile-and-a-half away from the rest of the wreckage. US investigators were yesterday moving towards the view that the explosion of an airliner 12 days ago was the result of an explosive device, as the nation reeled from Saturday's bomb at the Olympics. Although he is regarded as a maverick, his views are supported by many mainstream MPs in private.After the shadow Cabinet election results were announced last Wednesday, Mr Blair's spokesman said a long-running review of the rules of the Parliamentary Labour Party would lead to a new "code of conduct" for Labour MPs and new arrangements for "consultation" in government.Defence rebellion, page 2.