LAWRENCE, Mass. (AP) – Investigators interviewed witnesses and neighbors and combed the scene of the city’s largest fire in more than a decade Tuesday, trying to determine what caused the massive blaze that quickly spread through 16 buildings and left about 90 people homeless.

The seven-alarm fire started in an empty downtown nightclub in the predawn hours Monday, destroying homes and businesses. One minor injury was reported.

Twenty-three occupied residences were affected, and at least 15 residents spent the night in a Red Cross shelter, Red Cross spokesman Jamie Devlin said.

On Tuesday, members of a task force set up to investigate suspicious or unexplained fires in Lawrence interviewed witnesses they could not reach a day earlier, seeking to determine what happened in the day and evening before the blaze, fire Chief Peter C. Takvorian said. They also were looking for physical evidence of exactly where and how the fire started.

“But there is so much destruction on that site, that may take some time,” he said.

Takvorian said investigators could not examine the scene Monday because firefighters were still struggling to extinguish the blaze.

The task force, formed after a string of arsons in the city in the late 1980s and early 1990s, includes representatives from the federal Bureau of Alcohol, Tobacco, Firearms and Explosives, the state Fire Marshall office and Lawrence’s fire and police departments, Takvorian said.

Firefighters were hampered by wind chills that dropped to 2 below zero, freezing the water used to fight the blaze and covering buildings and streets in ice.

Also Tuesday, the Lawrence City Council was scheduled to meet to discuss Mayor Michael J. Sullivan’s call to raise property taxes and water bills to help cover a projected shortfall of up to $7 million in the city budget. Without the extra money, Sullivan warned that up to 20 firefighters would be laid off and two fire stations closed.

AP-ES-01-22-08 1511EST