WINDSOR, Colo. (CBS4) – Two contractors installing a sewer pipe for a new neighborhood were killed Tuesday night. Firefighters say they were buried alive after a working trench collapsed.

The men, later identified as Cristopher Ramirez, 26, of Boulder and Jorge Baez Valadez, 41, of Denver, were working near the intersection of Camberly and Whiteley drives, where D.R. Horton and Express Homes houses are being built.

“(The victims) were putting a utility line at approximately 15-feet-deep in the hole,” said Brandon Garcia, Battalion Chief for Poudre Fire Authority. “They were completely buried.”

Garcia said retaining walls often used to prevent such collapses at construction sites were not being used at the point where the men were buried.

Their names were released by the Weld County Coroner on Wednesday night. An investigation by federal, state and local authorities is underway. The formal cause of death for both victims will be determined by autopsy and laboratory results.

Ten emergency response agencies were dispatched to the scene including Windsor, Loveland, Poudre and Greeley fire departments. Crews spent more than seven hours working to extricate the workers.

When asked why heavy machinery in the area was not used to expedite the process, Garcia said such machinery would make the rescue more dangerous for everyone involved. Machinery in the area was shut down to prevent further collapse. Firefighters also did not want to injure the trapped victims with the machinery. The excavation had to be conducted by hand using small shovels and buckets to remove the soil from around the workers.

While one of the victims was presumed deceased early in the response, the other was able to speak with rescue teams during their efforts.

“(Rescue teams) had a PVC pipe down that provided air,” Garcia told CBS4’s Dillon Thomas. “We were 100 percent in the mindset that this would be a successful rescue.”

However, as the sun faded so did the likelihood of a successful rescue. One of the victim’s family was able to speak with him prior to his passing.

“We were able to bring up the family members, and allow them to talk to him,” Garcia said. “It was very much about, ‘We are here, and words of encouragement.’”