FEDERAL police across the United States are today hunting for American terrorists they believe may have been responsible for the Olympic Games bombing that killed a woman and injured at least 110 people. A crude pipe bomb packed with a kilogram of explosives blew up in Centennial Olympic Park, Atlanta, as 50,000 revellers enjoyed a late-night rock concert. A 40-year-old Turkish cameraman, Melih Uzunyol, died of a heart attack as he rushed to film the blast scene. Organisers insisted the Olympics would continue despite the outrage, which has left Atlanta in shock. 'The Games will go on,' said International Olympic Committee director Francis Canard. President Bill Clinton pledged to bring the attackers to justice: 'We will see that they are punished.' As competition resumed, 20,000 people stood in pouring rain at the Olympic Stadium to pay their respects to the victims for one minute. - after which heavy rock music boomed from the public address system. The homemade bomb was hidden in a leather satchel at the base of a tower holding lighting and sound equipment. It went off at 1.25 am, sending shards of glass and metal tearing through the terrified crowd. Atlanta officials believe many more could have been killed and injured if it had not been for an observant security man, known only as Richard. A calm-voiced caller, said to be a white American male, warned an emergency telephone operator of the impending blast 18 minutes earlier, a Justice Department official said. Shortly after the call, Richard spotted the satchel and immediately began ordering people to move away. The FBI found at least two additional suspicious packages in the park, which bomb squad members are investigating. The warning call was traced to public telephones in the park. As nervous athletes returned to their venues, FBI agents focused on America's burgeoning militia movement as prime suspects. Just three months ago, federal police raided a 'bomb factory' in rural Georgia where members of an extreme right-wing group, known as the Vipers, were caught making pipe bombs similar to the one that exploded yesterday. 'People were on the ground everywhere. There was blood all over the place,' said Willie Peters, whose mother-in-law was among the injured. Amanda Walachermire, 19, was just about to leave the park when the bomb went off. 'We were getting ready to go home when we heard a big boom,' she said. 'There was a lot of smoke, and then some security guys began screaming: 'Run! Run! Run!'.' A security source revealed that agents were working on the theory that the bombers were domestic extremists. 'This type of device would suggest that a group or individual from within the United States is quite probably responsible. At the moment this is the most likely scenario and the one we'll look at first,' he said. 'These devices are crude and - for anyone who wants to find out - easy to make. Someone can find the information by simply looking on the Internet.' Atlanta's Mayor, Bill Campbell, said several threats had been received during the Games. 'Our greatest fear was an act of terrorism - it happened,' he said. Pipe bombs generally involve small charges but are frequently packed with homemade shrapnel, such as nails, to maximise injuries in crowds. In the spring raid, a dozen members of the Vipers militia - who refuse to recognise the federal Government's authority - were arrested. They told authorities that at least 12 bombs were being made to disrupt the Games. 'We have reason to believe these bombs were to be used at some Olympic venues,' a source said in a claim later denied by officials seeking to play down security fears. The militia movement has been a constant threat to security in the US since the Oklahoma City bombing last year, which killed 168 people. FBI officer-in-charge, Woody Johnson, said security had been stepped up throughout the city after the bomb.