(CNN) - The National Transportation Safety Board will investigate a pressure increase detected in a natural gas pipeline north of Boston as it tries to figure out what caused a series of fires and gas explosions in three Massachusetts towns, NTSB Chairman Robert Sumwalt said Saturday at a news conference.
A pipeline controller working at a console in Columbus, Ohio, noticed the pressure increase in a pipeline in Lawrence, Massachusetts, one of the three towns where the fires occurred, Sumwalt told CNN's Alison Kosik. He didn't say when the pressure increase was noticed.
"Certainly we will interview that pipeline controller," he said.
The NTSB, which is investigating because transportation -- in this case, of natural gas -- was involved, arrived in Massachusetts on Friday morning to investigate the fires and gas explosions and will also be looking into the system procedures, operations, and safety culture of Columbia Gas and its parent company NiSource, as well as constructing a timeline of events surrounding the fires.
More than 60 suspected gas fires broke out Thursday evening in homes in the north Boston towns of Lawrence, Andover and North Andover. One person was killed, several were hurt and dozens of people were evacuated. About 18,000 customers lost power, National Grid reported.
"We are very interested to understand the operations of Columbia Gas. We will be looking at their record keeping, their procedural compliance, their procedures, their training, the oversight of their contractors," Sumwalt said Saturday.
Sumwalt also noted there are 14 gas pressure regulators in the area and that investigators plan to test all of them and make sure they are all operating properly. He expects that NTSB investigators will remain on scene for seven to 10 days while they collect perishable evidence and conduct interviews.
"Our mission is to find out what happened so we can keep it from happening again," Sumwalt said.
Sumwalt said they will work to determine a cause for the incident and issue a preliminary report, but that a full detailed report on the exact cause may not be complete for up to two years.
There is no evidence at this time that anything nefarious contributed to the fires, Sumwalt said.
State of emergency
Gas mains were shut down in the three towns. Hundreds of natural gas technicians were to descend on the towns in the coming days to restore gas service safely before electricity could be turned on, state officials said.
It's unclear when people who evacuated their homes will be allowed to return. Sumwalt said the Massachusetts Department of Public Utilities and the gas companies will make that decision, not the NTSB.
Jeff Hall, a spokesman for the Red Cross, said Friday there were almost 400 people shelters after the Thursday night explosions and fires.
"The evacuations are in the thousands," Hall said Friday, adding he expects many residents were staying with friends and family in the surrounding area.
Massachusetts Gov. Charlie Baker declared a state of emergency Friday in the three towns and put another utility company in charge of restoration efforts. Baker said New England-based Eversource would replace Columbia Gas of Massachusetts.
Eversource tweeted Saturday that it was working to shut off more than 8,000 gas meters, and the company said it anticipated "this critical first phase will be substantially complete" Saturday night.
On Friday, the governor said Columbia was "simply inadequately prepared" to effectively manage relief efforts.
Mayor Daniel Rivera of Lawrence, one of the affected towns, said of the company, "It just seemed like there's no one in charge, like they're in the weeds, and they've never seen this before."
Utility President Steve Bryant later defended the company's performance, saying the company had remained in constant touch with state and federal officials.
"I would say that we've advanced this as rapidly as it could possibly be advanced," he told reporters. "I don't think that anybody else managing this would've been further down the road than we are at the moment."
Bryant expressed his condolences to the victim's family, apologized for the inconvenience to customers and said the company was providing "all the resources that we possibly can to be able to correct the damage."
'It looked like Armageddon'
Thursday evening, homes erupted in flames across the three towns, consumed by more than 60 suspected gas fires.
"It looked like Armageddon, it really did," said Andover Fire Rescue Chief Michael B. Mansfield.
One house in Lawrence exploded, sending the chimney flying. It crashed into a nearby car, fatally wounding a teenager who was inside. Leonel Rondon, 18, and two of his friends were in the car when the debris struck, his family told CNN affiliate WHDH. He later died at the hospital, authorities said.
As pressure mounted for gas company officials to provide answers about what happened, Sens. Ed Markey and Elizabeth Warren of Massachusetts called for a congressional hearing on the explosions and fires.
Utility works with officials to 'investigate this incident'
This is not the first time that a subsidiary of NiSource, the parent company of Columbia Gas of Massachusetts, has been the subject of a federal probe stemming from a disaster.
A Columbia Gas Transmission Corporation natural gas pipeline burst in West Virginia in 2012 and NTSB investigators determined that external corrosion, which could have been discovered by the pipeline operator, was at fault.
Columbia Gas Transmission was owned by NiSource until 2015, when the company was spun off into Columbia Pipeline Group. Later, that company became part of TransCanada.
NiSource is one of the largest natural gas utilities in the United States, serving more than 3.4 million customers in seven states, according to its website. The company also provides electric distribution, generation and transmission services to almost 500,000 customers in northern Indiana as well.
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