A secret entry door and videotaped images of several people inside a landmark Madrid skyscraper as it burned now suggest arsonists set fire to the Windsor building. Six days after the fire, television stations broadcast an amateur video shot by a resident of the area in which several people can be seen moving about the 16th floor as the flames advanced, some three hours after the structure was evacuated. Another local resident told local media that she too saw people moving around inside the building as it burned, and that they turned on, then off, the lights of some offices. Firefighting experts told local media that anyone who was in the building more than a few minutes after it caught fire would have needed an asbestos suit, otherwise they would have not been able to stand the high temperatures. The daily ABC quoted investigators as saying the images appear to depict individuals wearing helmets, and that at least one of the silhouetted figures appears to be talking into a hand-held radio.Two other papers, El Mundo and La Razón, report in Tuesday's editions that a secret passage into and out of the building has been discovered. The door appeared to have been forced open. "The discovery of this secret door indicates that someone could have entered and exited the building without being seen the night the flames devoured it," said La Razon. The Tele 5 television station claimed investigators now believe the fire was probably started deliberately. Under the headline 'The Mystery of the Windsor Grows' another paper published photographs showing two separate blazes in the building, one four floors below the other.