CAÑON CITY, Colorado (AP) — Police in a small Colorado town have launched an investigation into a “green” funeral home following the gruesome discovery of 115 decaying bodies in a neglected building.

The probe was launch after a report was made that an awful smell was seeping from the building for days.

Investigators were tight-lipped Friday about exactly what they found inside the Return to Nature Funeral Home in Penrose, Colorado, but their plans to bring in teams that usually deal with airline crashes, coroners from nearby jurisdictions and the FBI pointed to a grim mess.

A state document, meanwhile, alleged funeral home owner Jon Hallford tried to conceal the improper storage of corpses. He claimed he was doing taxidermy at the facility, according to the state suspension letter dated Thursday.

Hallford acknowledged that he had a “problem” at the property, the Colorado Office of Funeral Home and Crematory Registration letter said. The document did not elaborate on the taxidermy and alleged improper storage of remains, but the facility’s registration has been expired since November.

No one had been arrested or charged. Text messages to the funeral home seeking comment went unanswered. No one at the business picked up the phone and there was no working voicemail.

Funeral home officials were cooperating as investigators sought to determine any criminal wrongdoing, Fremont County Sheriff Allen Cooper said at a news conference where he called the scene inside the building “horrific.”

On Friday, a sour, rotten stench still came from the back of the building, where windows were broken. Coroner’s officials from Fremont County and nearby El Paso County parked their trucks outside and discussed among themselves as they walked around the building.

Some identifications would require taking fingerprints, finding medical or dental records, and DNA testing in a process that could take several months, Fremont County Coroner Randy Keller said. Families would be notified as soon as possible after body identification, he added.

Family members who have used the funeral home were asked to contact investigators.

The FBI was bringing in teams with additional training and specialised equipment that process “scenes of national magnitude,” such as major airline disasters, Denver-based FBI Special Agent in Charge Mark Michalek said.

The bodies were inside a 2,500-square-foot (230-square-metre) building with the appearance and dimensions of a standard one-story home. The funeral performed burials without embalming chemicals or metal caskets, using biodegradable caskets, shrouds or “nothing at all,” according to its website.

The company charged $1,895 for a “natural burial,” not counting a casket or cemetery space, and until July offered cremations, too.

Under Colorado law, green burials are legal but state code requires that any body not buried within 24 hours must be properly refrigerated.

Deputies were called in Tuesday night in reference to a suspicious incident officials haven’t yet described. Fremont County Sheriff’s Office investigators returned the next day with a search warrant and found the remains.