By ANDREW DAMPF MILAN, Italy (AP) - A small plane, in flames and sending a distress signal, smashed into the tallest skyscraper in Italy's financial capital Thursday, raising fears of a Sept. 11-type terror attack. At least five people were killed and 60 injured, but the Italian government said it was probably an accident. The aircraft punched through the 25th floor of the slim Pirelli building, gutting two floors and starting a fire that sent smoke pouring out into the clear blue sky over downtown Milan. Emergency workers helped bloodied men in business suits while firefighters worked to put out the blaze. "I heard something like the engine of a plane dying out, and then I heard a terrible explosion," said Raffaele Taccogna, who was tending bar at the nearby Atlantic Hotel. "I certainly thought of the September attacks in the United States," he said. "It really looked like the same thing." The pilot - who was on a 20-minute flight from Locarno, Switzerland, to Milan - issued a distress signal and reported problems with the plane's landing gear moments before plowing into the 30-story building at 5:50 p.m., Milan police officer Celerissimo De Simone said. One witness, Fabio Sunik, said the plane was on fire before it crashed. The plane did not try to change course, "but just went straight in," said Sunik, a sports journalist. "Then I saw rubble falling from the building." Milan's main train station, about 200 yards away from the skyscraper, was evacuated for security reasons, and no trains were running from there. After-hours trading was suspended on the Milan stock market, which was already closed for the day. President Bush was quickly notified of the collision, press secretary Ari Fleischer said. The FBI was assisting in the investigation. In Washington, a senior Bush administration official, speaking on condition of anonymity, said Italian officials had told the United States that a mechanical problem not related to terrorism caused the crash. Interior Minister Claudio Scajola told reporters in Rome that "initial reports point to an accident." "We believe it isn't a terrorist attack," said police Sgt. Vincenzo Curto, reached at Carabinieri headquarters. Some 1,300 people work in the building, which houses local government offices, but it was not known how many where still there when the crash took place - not long after working hours ended. The five dead were the pilot, two workers in the building and two passers-by, said Carlo Leo, a civil defense official. Rescue workers found a survivor, three hours after the crash, on the 25th floor, where one of the dead was found. The pilot, believed to be the only one in the plane, was identified by police as Luigi Fasulo, a resident of Pregassona, Switzerland who was thought to be in his 60s. The plane was a Rockwell Commander, said Patrick Herr of the Swiss air traffic control office SKYGUIDE. Swiss television identified the model as a Commander 112TC, a twin-engine craft with a 35-foot wingspan not produced since 1979. A woman who worked on the eighth floor said she saw 10 people who were bleeding. Emergency workers in bright orange uniforms helped a man walk from the scene, his shirt splattered with blood and his hand covering a gash on his head. An unspecified number of people were rescued from elevators in the building, the Italian news service ANSA said. Some 20 people were taken to Fatebene Fratelli hospital, officials there said. Among them was a woman with serious burns. The collision damaged a building seen as the symbol of Milan, the heart of Italy's financial and industrial world. Built in the 1950s, the 415-foot-high building once housed the headquarters of the tire giant Pirelli. Smoke continued to pour out of the building for three hours after the crash, though firefighters quickly controlled the blaze. A large section of an entire floor lost its walls. Smoke and liquid poured from the gash in one side of the building. Luccheta Antonio, 52, a barber down the block, said: "It was shocking. The windows shook and the mirrors fell to the floor." Police cordoned off the area as people gawked at the skyscraper. Senate President Marcello Pera said initially that it appeared the crash was "most probably" a terrorist attack. But later, Pera's spokesman said the Interior Minister had advised that apparently was not the case. The State Department had warned of possible terrorist attacks in Milan and three other Italian cities over the Easter weekend. But U.S. authorities had no recent intelligence suggesting any kind of terrorist attack was imminent in Milan, said a U.S. official, also speaking on the condition of anonymity.