"There were billows of smoke coming from Lawrence behind me. I could see pillars of smoke in front of me from the town of Andover." Governor Charlie Baker said state and local authorities are investigating but that it could take days or weeks before they turn up answers. Residents cover their face from the smoke while being evacuated from homes as firefighters battle a fire in Lawrence, Massachusetts. Credit:AP "This is still very much an active scene," he said. "There will be plenty of time later tonight, tomorrow morning and into the next day to do some of the work around determining exactly what happened and why." State police put the tally of fires and explosions at 70, up from the 39 initially reported. State police received between 60 and 100 reports of fires and gas explosions in the Merrimack region.

The cause of the explosions wasn't immediately clear. Emergency crews are scrambling to douse house fires in Lawrence, Andover and North Andover, north of Boston, and gas and electricity lines are being turned off in an attempt to stop further damage. Firefighters battle a large structure fire in Lawrence, Massachusetts, a suburb of Boston. Credit:WCVB via AP Lawrence General Hospital said it was treating four victims with injuries related to the fires but did not provide details about their conditions. Jill McDonald Halsey, chief of marketing and communication, told The Washington Post. "We are in emergency management activation mode and are ready for any more that come."

Massachusetts State Police say troopers have been dispatched to the three towns to secure scenes and help traffic that has snarled roads as panicked residents attempt to flee their suburbs amid the afternoon peak hour. A man whose neighbourhood was among dozens that erupted in fire says he ran into his basement to find that the room was glowing. Lawrence resident Ra Nam says he was in his yard when the smoke detector in his basement went off around 4.30pm on Thursday, local time. When he ran downstairs and saw the boiler on fire, he quickly grabbed a fire extinguisher and put it out. Minutes later, Nam said he heard a loud boom from his neighbour's house and the ground shook. Nam said a woman and two kids had made it out of the house but the basement was on fire. Lawrence resident Bruce Razin was among the evacuees standing outside the Colonial Heights neighbourhood near the city's high school trying to decide what to do next.

Officials had cut power in the area and the streets were pitch black, save for emergency vehicle lights. Razin said he arrived just as residents were being evacuated, and immediately saw the house two doors down was leveled from an explosion. "I couldn't imagine if that was my house," said Razin, who purchased his home nearly two years ago. "It's total destruction. I'd be completely devastated." With a backpack filled with personal items he had hastily grabbed, he said he'd head to his mother's home a few towns over for the night. Firefighters battle a house fire in North Andover, Massachusetts. Credit:AP

The Massachusetts Emergency Management Agency blamed the fires on gas lines that had become over-pressurised, but officials who responded to the area were still investigating the cause. State officials said Columbia Gas was working to ease pressure on gas lines following the fires. Columbia had announced earlier on Thursday that it would be upgrading gas lines in neighbourhoods across the state, including the area where the explosions happened. It was not clear whether work was happening there on Thursday, and a spokeswoman did not immediately return calls. Reached by phone, some local officials described scenes of panic as residents rushed to evacuate, many wondering if their homes would be next to erupt in flames. In North Andover, town selectman Phil Decologero said his entire neighbourhood had gathered in the street, afraid to enter their homes. Just a few streets down, he said, homes were burning. "It's definitely a scary situation at the moment," he said. "It's pretty severe." Aerial footage of the area showed some homes that appeared to be torn apart by blasts. At one, the upper portion of a brick chimney crushed an SUV parked in the driveway.

Multiple fire trucks from surrounding communities arrive in Lawrence, Massachusetts. Credit:AP Schools and senior citizen centres were being opened as gathering points for residents who fled their homes. Lawrence City Councillor Marc Laplante said entire neighbourhoods were being evacuated in the Colonial Heights area, which he represents. "People need to get out of this area safely," he said at the time. "It's really difficult because the traffic right now is horrendous." Joseph Solomon, the police chief in nearby Methuen, said 20 to 25 homes were on fire in Lawrence when he responded to help. He said there are so many fires "you can't even see the sky." Officials in Andover, a town of 35,000 residents had advised all residents and businesses to evacuate and to shut off their gas, if they know how to safely. Soon after 7pm, officials said all fires in the town had been extinguished.

Around the same time, State Police said electricity was being shut off for all residents in Lawrence, North Andover and Andover, where some were still reporting an odour tied to natural gas. The three communities house more than 146,000 residents about 40 kilometres north of Boston, near the New Hampshire border. Lawrence, the largest of them, is a majority Latino city with a population of about 80,000. The Massachusetts Emergency Management Agency said staff members were heading to Lawrence, Andover and North Andover, along with state fire investigators. AP