KEY WEST (CBSMiami) -- Three men collapsed and died while working underground on a road project in Key Largo Monday morning.
The men who died were working near Mile Marker 106 after residents complained about smells coming from a drainage manhole, according to Monroe County Sheriff Rick Ramsay.
Monday evening, authorities released the names of the deceased workers. The youngest was 24-year-old Robert Wilson of Summerland Key. Thirty-four-year-old Elway Gray of Fort Lauderdale and 49-year-old Louis O'Keefe of Little Torch Key died in the manhole.
A law enforcement source told CBS4's Peter D'Oench this was a chain reaction. One worker went into the manhole and collapsed because of gasses. A second worker went into rescue him and collapsed as well. The same thing happened to a third worker who tried to help him.
Ramsay said the men were overwhelmed by a combination of methane and hydrogen sulfide gas coming out of the 15-foot deep hole. It's something he says is concerning since manholes such as that one should be properly ventilated and it appeared it had ventilation problems. The levels of oxygen in the manhole were not enough to sustain life.
"Generally, you want to ventilate the tube out before you go in there and have proper breathing stuff. It appears there was no venting done prior. The best we can see at this time, there was no pre-venting going in and obviously going into a contained space like this where there's no gasses, it can be deadly as we saw today," said Ramsay.
Tasha Occhiuzzi lost three co-workers in the incident.
"I don't believe it. I still can't believe it. No, it's our family, these families," said Occhiuzzi.
The deadly incident happened, around 8 a.m., when one of the workers went inside the manhole to find out why the newly paved Long Key Road was settling in a certain spot. While in there, he got stuck.
Three other workers tried to help the trapped worker. The group included a volunteer firefighter with Key Largo Volunteer Fire Department and two Monroe County Sheriff's Office deputies.
The firefighter who went underground also collapsed and had to be rescued.
"One firefighter decided to take his air pack off to attempt a rescue. He succumbed to gas as well," said Ramsay.
Sources say a second firefighter took off his air tank and carried it between his legs so he could be lowered into the manhole.
"The firefighter brought him. He was unconscious and not breathing," said Ramsay.
The firefighter and the three workers were pulled from the hole, according to Monroe County Sheriff's deputies.
Three workers were confirmed dead at the scene. Deputies were able to revive the firefighter and airlift him to the Ryder Trauma Center where he, at last check, was under an induced coma.
Three Sheriff's deputies who were exposed to fumes were taken to Mariner's hospital for treatment.
A fourth worker was treated at the scene.
Residents at the end of Long Key Road were evacuated out of precaution, city officials said. By 2 p.m., they were allowed to return home after tests showed it was safe for them to do so.
"Well it was just kind of confusion that I think there were people down in the manhole and they had to get them out of there because there was bad gas or they said toxic fumes or something. We live right there and we were evacuated," resident Linda Seymour told CBS4's Peter D'Oench.
"I think it's horrible and I think we need to be praying for them and their families," said another resident who had been evacuated.
The sheriff's office said the three employees who died were working for Douglas N. Higgins doing underground work as part of street repairs. CBS4 reached out to the Douglas N. Higgins company in Palm Beach Gardens for a statement but, so far, has not heard from the company.
A very emotional Occhiuzzi told D'Oench that those who died were all family people.
"They'd do anything for you. They'd pack your lunch, make your lunch. We're a family working together, not just the Higgins family," said Occhiuzzi.
The Monroe County sheriff's office and officials with OSHA, or Occupational Safety and Health Administration, are investigating the case.
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