Firefighters from several states were helping in the rescue effort

'Human tissue' found in elevator tunnel, but source is unclear

• Owner: Air pockets could be keeping men alive
• Rescuers include OKC bombing veterans
• Trapped men were cleaning tunnels
• 'Thudding sounds' heard earlier
• Families get hourly briefings
• Related stories and sites

HAYSVILLE, Kansas (CNN) -- Four people trapped in a grain elevator since an explosion Monday could be alive if they found air pockets inside the tunnel they were cleaning, elevator owner Paul DeBruce said Tuesday.

A fire official said he was optimistic the men will be rescued, possibly late Tuesday night.

Meanwhile, searchers Tuesday evening discovered "human tissue" in the tunnel, but it was unclear if it was from one of the two men killed in the explosion or from one of the trapped workers, officials said.

Officials have yet to determine the cause of Monday's grain dust explosion, which left two dead and at least nine others injured at the DeBruce Grain Elevator in Haysville, Kansas.

Rescuers include OKC bombing veterans

Rescue crews, working in two shifts around the clock, are digging through tons of grain that continues to flow down to where the men are believed to be trapped.

Dozens of rescuers, many of them veterans of the Oklahoma City bombing, are progressing at about 25 feet an hour and have dug 600 feet into the 800-foot section of tunnel, District Fire Chief Ken Cox said.

"There's a good chance of bringing them out alive," Cox said. Search dogs have indicated they smell a human scent, raising hopes. Searchers also were using ultrasound and infrared equipment to look for the men.

"We have not given up ... we are going to keep working on it," DeBruce said. "We are making some progress, we think, in getting into some of the tunnels."

Trapped men were cleaning tunnels

Three of the four trapped men were temporary workers hired to clean the elevator's tunnels. They were sweeping and cleaning a 7-by-8-foot tunnel when the blast occurred, DeBruce said.

DeBruce said air spaces, or "voids," are likely inside the tunnels, which could keep the workers alive.

Sedgwick County Fire Chief Joe Piper said the men are believed to be trapped in one of two tunnels running beneath the 120-foot tall towers of the grain elevator. Each tunnel is 1,200 feet long. The four are believed to be trapped in an 800-foot section of one tunnel.

Fire Department spokesman Fred Ervin briefed families of the workers and said crews are working "as fast and as hard as they can" to find the missing men.

'Thudding sounds' heard earlier

Earlier, rescuers heard "thudding sounds" in the area where the four are believed to be trapped, but Ervin said "at this point, we have not heard anything."

"It is really slow at this point because of the debris inside the tunnels, grain and rock and that kind of thing. Crews are having to hand dig, and that slowed the search some, but it is progressing," he said.

Ervin said while the situation remains bleak, rescuers hope the four workers will be brought out alive.

"If you think back to the Oklahoma bombing, people were found several days after that," he said. Rescue crews are able to breath inside the tunnel, "so that is a good sign. They are able to breathe in the tunnels and hopefully those that are still trapped inside also have ample air."

Families get hourly briefings

The families of the trapped workers gathered at the Oatville Elementary School and were being given hourly briefings on the search, Ervin said.

Officials assured them the rescuers helping local crews are the nation's best -- eight members of the Oklahoma City Fire Department and 62 from a federal rescue squad that worked at the 1995 federal building bombing site.

On Monday, a crane and helicopters were used to rescue six people from the roof of the huge elevator complex, located five miles south of Wichita.

Of the nine people hospitalized, five were in critical condition and four were in serious condition, Piper said.

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