on the metal, causing it to fail. The age of the pipe, and the difficulty of inspecting underground infrastructure, made corrosion a possible factor as well, but a New York State safety official reported at a Public Service Commission meeting in September 2007 that there was "no indication that the pipe was deteriorated or weakened by corrosion." Leaks There had been persistent steam leaks and related repair activity in the area the weeks and months prior to the explosion, and utility crews had checked the site only six hours before. Preliminary investigation results showed that a leaking seam repaired just before the disaster was found intact, and the pipe burst suddenly at a location approximately 10 feet (3 m) away. Robert Caligiuri, an engineer for Exponent Engineering, blamed the rupture on a "crack-like flaw" in a welded seam in the pipe wall, in a preliminary engineering report released on October 23, 2007, that was commissioned by attorneys representing the tow truck driver badly burned in the explosion. He stated, "The observed crack-like flaw appears to be old and is large enough that, in my opinion, Con Ed should have detected it prior to the rupture. Once detected, good and accepted practices would have required that this pipe section be immediately replaced." The utility called the report "misguided" and said in a statement that, "our independent consulting engineers have determined that there was no degradation in the condition of the pipe prior to the rupture," and "the weld in this instance in no way contributed to the rupture. The weld was forced open when the rupture occurred; it was not the cause of the rupture." Asbestos Pipes of that age often were wrapped in asbestos, a known human carcinogen, and the site was declared an "asbestos containment area." Although some asbestos was later found in the solid debris, no friable particles were detected in any of the air samples. However, anyone entering the containment zone was still required to wear a respirator and protective clothing during the clean-up. This caused some to openly question the air test results, particularly since false reassurances on air quality were given by officials after the September 11 attacks. More than 100 people evacuated by rescue workers, and the workers themselves were hosed down, and had their clothes taken for testing at a decontamination area. People in the affected area who self-evacuated were initially advised to