GREELEY, Colo. -- After a five-day investigation by federal authorities into the Jan. 13 fire at the Nugget International building in Greeley, authorities revealed there is no indication the fire was arson-related.

The authorities said there was no sign of any incendiary device in the building. Several possible accidental causes were located within the area of the origin of the fire, according to the federal authorities' report.

Officials from the Federal Bureau of Investigation; the Alcohol, Tobacco and Firearms; and the Environmental Protection Agency jointly conducted the investigation.

The federal authorities findings squash any speculation that the fire may have been started by an animal-rights group.

"We're happy about that," Greeley police spokesman John Gates told 7News. "There has been a lot of speculation over the past week that (the fire) was arson and certain groups were identified. The results of this investigation points out the need to remain objective. We're pleased it doesn't appear to be a criminal act in this case."

Due to the total destruction of the building by the intense, long-smoldering fire, the investigation could not determine the exact cause of the fire, Greeley police said.

Nugget International is the largest lambskin processing plant in the country, according to Greeley police. The building was owned by Con-Agra and leased to Nugget International. The structure is about 50,000 square feet in size and was a total loss.

Existing inventory inside the building at the time of the fire included about 135,000 lambskins and 250,000 pounds of wool.

The fire smoldered for several days, as can be seen by the picture to the left. It was the largest fire in Greeley history from a standpoint of financial loss, Gates affirmed.