Abstract: TWO EMPLOYEES WERE CUTTING OUT A 3' BY 3' SECTION OF A CORRUGATED METAL PIPE WHICH ENCLOSED A 12" WATER PIPE. THEY WERE USING A GASOLINE POWERED CUT-OFF SAW WITH AN ABRASIVE CUTTING BLADE. A FLAME APPEARED AT THE CUT POINT AND WAS EXTINGUISHED WITH WATER. THE EMPLOYEES THOUGHT THE BURNING MATERIAL WAS TAR ASPHALT ON THE CORRUGATED PIPE. THE EMPLOYEES TOOK A HALF HOUR LUNCH BREAK, THEN RESUMED CUTTING THE PIPE. AFTER ANOTHER 50 MINUTES OF CUTTING, THE FLAME REAPPEARED. AS THE EMPLOYEES BEGAN TO PUT WATER ON THE FLAME, AN EXPLOSION OCCURRED. ONE EMPLOYEE RECEIVED FACE BURNS, A FOOT INJURY, AND A BROKEN KNEE CAP. THE SECOND EMPLOYEE RECEIVED TORN LIGAMENTS AND BURNS ON BOTH LEGS. A GAS LINE WAS LOCATED ABOUT 30' FROM THE WATER PIPE. SOME OF THE NATURAL GAS MAY HAVE SEEPED INTO THE CORRUGATED PIPE, WHERE IT ACCUMULATED.