reporter: the collapse, authorities suspect, triggered by a buildup of methane gas. a massive response from emergency teams working to free those inside. certain areas right now are unsafe to enter due to the structure. reporter: teams quickly able to rescue eight employees. 20 minutes after arriving, crews rescue another employee. on a stretcher, he s rushed to medics. but one man remains trapped. his leg, fractured, dangerously pinned underneath all of that heavy debris, unable to move. it s a concrete building. concrete walls, concrete roof, concrete i-beams on the ceiling. so, the gentleman that was pinned severely was trapped by the concrete truss. straight down, pancake collapse. reporter: some 70 firefighters and rescuers working to burrow through the concrete. some on their hands and knees, others with their ears pressed against the rubble until finally, they are able to reach the remaining employee. we tunneled in about 40 feet, six feet below the collapse. we used