A year after a fire that swept through an Anchorage apartment building, killing three people, federal authorities have released an overview of extensive testing conducted as an investigation of the blaze continues.

Jason Chudy, a spokesman for the U.S. Bureau of Alcohol, Tobacco, Firearms and Explosives, said the bureau’s Fire Research Laboratory in Maryland has been helping the Anchorage Police and Fire Departments look into the Royal Suite Lodge fire on Minnesota Drive. The Feb. 15, 2017 early-morning fire killed 38-year-old Teuaililio Nua, 63-year-old Vivian Hall and 70-year-old Laura Kramer, and displaced dozens of other residents.

“The full-scale tests were focused on helping investigators evaluate hypotheses related to the origin and cause of the fire,” Chudy wrote in an email. “The tests were based on information that was documented during the initial scene exam conducted in February 2017, an evidence exam that took place in May 2017, as well as follow up work performed by the Anchorage Field Office and Anchorage Police Department.”

Some of the main elements of the testing took place in October, according to Chudy.

“The tests included two full-scale wood structures and were documented using instrumentation to measure temperature and heat flux, along with digital video and still photographs,” Chudy wrote. “Reports are in progress and will be turned over to APD when complete.”

Nobody has been charged in connection with the fire, but Anchorage police have said an investigation of the fire is ongoing. APD spokeswoman Renee Oistad said the department had “nothing to add at this time” Thursday morning.

Police are still asking for any help citizens can provide in the investigation. Tips on the fire can be submitted to APD at 907-786-8900, or Anchorage Crime Stoppers at 907-561-STOP or through its website.

Shannon Ballard contributed information to this story.

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