One person is dead after a catastrophic gas line failure sparked chaos across the Merrimack Valley Thursday, igniting dozens of fires, causing explosions, and forcing the evacuation of two towns and part of a city. 

The massive emergency — and the frenzied response — sent several people to local hospitals and damaged some 60 to 100 homes, officials said. The rush of firefighters, police and ambulances across the region, as well as mutual aid rushing into the Valley, created widespread gridlock on local roads and on Interstate 495. 

One death was confirmed in Lawrence by police. A house on Chickering Road exploded early Thursday evening, shaking the surrounding ground. Parts of the chimney fell on a car, striking Leonel Rondon, 18. He was pronounced dead at Massachusetts General Hospital.

At a press conference in Lawrence late Thursday, Gov. Charlie Baker encouraged people to leave South Lawrence, Andover and North Andover. Baker told residents “just trust me, if you stay at home, you’re at risk.”

Baker addressed reporters with Lt. Gov. Karyn Polito and leaders from the three affected communities: Mayor Dan Rivera and Town Managers Andrew Maylor and Andrew Flanagan. Columbia Gas, the owner and operator of the lines that sparked the widespread flames, did not attend the press conference. 

The officials said they could not assure anyone “what the risk is at this point” and could not say how long the evacuation order would be in effect, but that no one should expect to return home Thursday night. 

“Our main concern is to provide shelter and to ensure our communities are safe,” Baker said. 

Thousands of residents were left homeless Thursday night after being evacuated. Emergency shelters were set up across the Valley, and the Red Cross was on site to help. At least one local hotel opened its rooms to evacuees free of charge.

It was not immediately clear Thursday how many people suffered injuries as a result of the fires, but as of 9 p.m., Lawrence General Hospital had treated 10. Jill McDonald Halsey, spokeswoman for the hospital, said at least one patient was in critical condition and another was in serious condition. She said the injuries ranged from smoke inhalation to blast trauma. 

In Lawrence, the sky held a thick haze from the dozens of fires across the city. At least four different helicopters hovered overhead while fire trucks criss-crossed the narrow streets. Firefighters stayed at smaller fires for only a few minutes, quickly leaving to address new blazes. 

Fire companies from across Massachusetts and New Hampshire poured into the Valley to help — including police and firefighters from Boston. 

Crowds poured out of their homes and packed the streets, heeding evacuation warnings and watching firefighters at work. Many were on the phone, making plans to stay the night with nearby family members. 

Sheila Doiron, a spokeswoman for Columbia Gas, said she had been stuck in traffic on the highway for hours trying to get to Lawrence. 

“We’re still determining the issue and still trying to make the area safe,” Doiron said. She did not answer when asked to explain what had happened, but said the company was still investigating. 

By 8 p.m., Columbia Gas crews were still working to stop the flow of gas to the region. The continued flow of fumes only exacerbated the crisis, which was still raging some four hours after it began. 

“It’s not a switch,” she said. “We have to shut off different systems of valves. ... It’s a process to shut it down in a safe way.”

Baker said the work to restore the communities was far from complete.

“The gas company folks are here. The response so far as been adequate. If I were to give it a grade, it would be incomplete because we have a lot more to do,” Baker said. “We have a lot of work to do for these homes that were destroyed or severely damaged.”

Police officers will be stationed at all major intersections throughout the night while the traffic and street lights are out. All schools in Lawrence, Andover and North Andover will close Friday. Courts in Lawrence are closed as is Merrimack College in North Andover.

“Lawrence is a resilient community. At the end of the day we’ll get through this,” Rivera said. He added that everyone south of the river should evacuate, but those to the north of the Merrimack should not be experiencing problems. 

Rivera said he received an email from the White House expressing concern. Boston Mayor Marty Walsh also expressed his support via Twitter.

Maylor said 12-14 homes in North Andover were impacted. Flanagan said Andover had seen “at least 30 fires.”

Baker said the two main questions he has for Columbia Gas are when it will be safe for residents to return and when they can expect to get power back.

“We don’t expect more fires tonight,” Baker said. “The depressurization of the lines and the shutdown of power is designed specifically so there are no more fires.”

The scope of the emergency was difficult to quantify Thursday. It is likely that the recovery for each of the three communities will take weeks, if not months.