ST. PAUL -- Investigators have determined a massive blaze that destroyed a hotel project under construction in downtown St. Paul last week was arson.

The federal Bureau of Alcohol, Tobacco, Firearms and Explosives announced that determination Tuesday, along with the St. Paul Fire Department, St. Paul Police Department and Minnesota state fire marshal's division.

Investigators concluded the Aug. 4 fire was intentionally set after investigating the scene, reviewing video footage and talking to witnesses. A four-day search found no human remains, and no one was unaccounted for.

The ATF sent members of its National Response Team to assist in the investigation. Investigators continue working on the case.