An investigation is under way at a Denver bar after the building was reportedly set on fire early Wednesday morning. According to police, five people were believed to have been killed inside before the fire had even started.

Commander Ron Saunier, of the Denver police, said authorities believe that a fire was set to the building to cover up the homicides.

While Saunier would not go into specifics as to what type of trauma they believe led to the death of the four women and one man inside of Fero's Bar & Grill, authorities did speculate that the victims were dead before the building had been set ablaze.

"We're not sure the exact nature of the trauma," Denver Police Chief Robert White, told ABC News affiliate KMGH.

"More than likely [this was] an attempt to conceal the homicide with an arson," Saunier added.

Reports from the scene indicate that the fire broke out shortly before closing time at the bar around 1:50 a.m. Wednesday morning.

Police are seeking help from anyone who was at Fero's Tuesday night, as they try to collect information on the victims and any possible motive or suspect.

The incident is being investigated as an arson-homicide, and police do not yet have any suspects, they said.

During a press conference at 8 a.m. this morning, police said no witnesses or bar patrons had yet come forward to talk to police, ABC News reports.