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.

In a statement, CEO Anne Behrendt of Doran Companies, the general contractor on the $69 million Seven Corners Gateway project, said company officials are “extremely disappointed” to learn that the fire was set intentionally.

“This destructive act is a considerable setback to a project that was moving the economy forward and supporting construction workers during this time of economic uncertainty,” Behrendt said.

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