By CLAYTON SANDELL, ABC News

(DENVER) — Three male teenagers were arrested Wednesday in connection with a mysterious six-month-old arson in Colorado that killed five members of a Senegalese family, including a toddler and an infant.

Two of the juveniles are 16 years old and one is 15, Denver Police Chief Paul Pazen said.

“These are the individuals that we believe are responsible for this horrific crime,” Pazen said at an afternoon news conference in Denver.

On Aug. 5 at around 3:30 a.m., police say three suspects in eerie face masks approached a house not far from Denver International Airport in darkness, igniting a fire that trapped people inside and burned so intensely it damaged neighbor’s homes on both sides.

Djibril Diol, 29, his wife Adja Diol, 23, and their 2-year-old daughter Khadija were killed, along with Djibril’s sister, Hassan, and her infant daughter, Hawa. Friends and family say Adja, Khadija, Hassan and Hawa had recently immigrated to the United States from Senegal.

The suspects, who were not identified because of their ages, are facing a litany of charges including first-degree murder, attempted murder, first-degree assault, burglary and arson. Police say they were taken into custody at their homes in nearby Jefferson County. They are not related, but police say the three knew each other.

Pazen would not discuss the alleged suspects’ motives, citing a desire to protect the integrity of the investigation and achieve a successful prosecution. However, Pazen said investigators concluded that race does not appear to be a factor in the crime.

“The evidence that we have uncovered and the circumstances and facts that we have found do not indicate that this is a bias-motivated crime,” Pazen said.

The case put the Senegalese community on edge as it went unsolved for months, despite a reward that grew to $50,000 and appeals by friends and family for tips. Police said they assigned two detectives to work the case full time and had help from the Bureau of Alcohol, Tobacco, Firearms and Explosives as well as the U.S. Secret Service.

“They have done an unbelievable job on this. There was very limited information that we had,” Pazen said. “This was as complex an investigation as I’m aware of in my entire career. And they did an amazing job.”

Community members who had grown increasingly frustrated at the apparent lack of progress praised investigators after Wednesday’s arrests.

“We are grateful, but we are still in pain,” said Papa Dia, founder of the African Leadership Group and a family representative. “Arrests have been made, but we know it’s not going to bring these beautiful people back.”

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