One person suffered minor injuries.
An ambulance crew on an unrelated call spotted the fire about 2:30 a.m., state Fire Marshal Stephen Coan said. The fire started in a nightclub that was being renovated and spread quickly on a stiff wind through the block that included early 1900s wood-framed buildings.
The club had no walls, and that "gave the fire an opportunity to take hold very quickly," Coan said.
Fire officials in Lawrence, about 30 miles north of Boston, said the cause was suspicious. Coan said state and city fire officials were investigating with agents from the federal Bureau of Alcohol, Tobacco, Firearms and Explosives.
Some people were clad only in pajamas as they fled into the bitterly cold morning, with chills below zero. Water sprayed by firefighters froze, covering buildings and streets with ice.
Zulma Borgos, 49, said she was awakened by calls of "Fire!
Fire!" from her boyfriend, Elias Riverra. Borgos said that when she looked out the window, "I couldn't believe what I saw."
"It was a ball of fire," said Riverra, 21. He didn't even have time to grab a pair of socks before waking Borgos' three girls in the apartment and running.
The girls, ages 5 to 12, were wrapped in blankets when they arrived at a Red Cross shelter set up in a school. Other people arrived in bathrobes and slippers.
About 150 people were evacuated from the area and 54 were at the shelter Monday afternoon, police Lt. Scott McNamara said.
"A lot of these people who were burned out today don't have anything," said Bill Meagher, a Red Cross volunteer. "They're not going to be able to find housing right away. With the freezing cold weather ... all the shelters are full."
The temperature was 12 degrees, and the wind made it feel like 2 below zero, the National Weather Service said.
