FARMINGTON — One firefighter is dead and at least six other people were seriously injured when a powerful propane explosion leveled a new building after crews arrived to investigate the smell of gas there on Monday morning, officials said.

The Route 2 building, which houses a nonprofit agency that serves people with disabilities, was evacuated after the gas was detected, said Farmington Selectman Scott Landry.

The injured were taken to hospitals in Maine and Massachusetts. Maine Medical Center in Portland said it had admitted five patients, four of whom were being treated in the Portland hospital’s intensive care unit. One was being treated for less severe injuries.

Among those injured is Fire Chief Terry S. Bell Sr., who was taken by LifeFlight helicopter from the scene, officials said.

Others injured included three other firefighters, an employee of the nonprofit who is credited with getting several people to safety, and an ambulance worker, according to Stephen McCausland, spokesman for the Maine Department of Public Safety.

They suffered burns from the blast, according to Farmington Police Chief Jack Peck Jr.

The ambulance worker was treated for his injuries and released from the hospital.

The name of the firefighter who died has not been released pending notification of his family.

The building housing the offices of LEAP Inc., which serves people with cognitive and intellectual disabilities and had recently opened, Landry said. A hole in the ground is all that is left of the building.

“It’s a war zone. It’s just a mess,” Landry said. “The building is gone.”

A maintenance worker has been credited with getting several people to safety before the explosion.

Larry Lord, of Jay, was able to get people out of the Life Enrichment Advancing People building, 313 Farmington Falls Road, Route 2, before the explosion leveled the building, according to Darryl Wood, executive director of LEAP.

Lord is being treated for multiple burns and was flown to Massachusetts General Hospital by LifeFlight, according to Wood.

Gov. Janet Mills, who is from Farmington, knew the firefighter who died, and went to the scene. “We’re going to get to the bottom of this as much as we possibly can, and make sure it doesn’t happen again,” she said in a tweet.

“Our hearts go out to all those impacted by this tragedy, especially to the loved ones of the firefighter lost and others injured,” she said.

Maine Medical Center said late Monday morning that it expects that some of the people injured in the explosion will be transferred to its Emergency Room in Portland.

“We have trauma teams on standby and have the resources and medical expertise needed to treat these patients,” the hospital said in a statement.

The blast around 8:30 a.m. was heard for miles and had enough force to blow a vehicle across an intersection. Paper, insulation and building debris rained on the area.

Multiple homes in the area were damaged, according to McCausland.

Several nearby businesses closed and the nearby Farmington Fair was closed for the day.

Steve Cutler, who lives about a half-mile away on Davis Road, said pictures fell off his walls and it “just shook the whole house.”

Cutler described the explosion scene as “complete chaos.” He went outside on his deck, got into his truck, and that’s when I saw “complete devastation.”

“It was white insulation, materials everywhere. I was dumbfounded,” Cutler said.

Kim Hilton, who works in the admissions department at the nearby University of Maine at Farmington, said there were scary moments after the blast occurred.

“It felt like someone hit our building with a vehicle,” she said.

The 40-by-60-foot, two-story building at 313 Farmington Falls Road, which served as the administrative offices for Life Enrichment Advancing People, opened eight to 10 weeks ago and wasn’t yet fully staffed, Landry said. The town had assessed the building’s value at $100,000.

The smell of gas was detected and the building evacuated before most workers had arrived for the day, he said.

Route 2 in that area was closed. Traffic was being detoured to Route 156.

According to McCausland, the body of the firefighter killed in the explosion will be removed from the rubble some time mid- to late-afternoon and taken to the Medical Examiner’s Office in Augusta.

This is the second firefighter to die in the line of duty in Maine this year. In March, Berwick Fire Capt. Joel Barnes died battling an apartment fire. Barnes, who is credited with saving a fellow department member’s life, was likely the first firefighter in Maine to have died in a fire in more than 38 years, public safety officials said at the time.

Just before noon, Sen. Susan Collins issued a statement saying “I am absolutely heartbroken to hear that a firefighter was killed and several others were injured in a terrible explosion responding to a call in Farmington this morning.”

She wrote, “I am praying for the firefighters and their families as well as the civilians who were hurt in today’s explosion. We can never repay our debt to the brave men and women like these firefighters in Farmington today who put their lives on the line to keep us safe.”

Sen. Angus King also issued a statement, saying he is “devastated by the news of the serious explosion in Farmington,” and that “my thoughts are with the first responders working at this moment to control this blaze, the family of the fallen firefighter, and the Franklin County community.”

Rep. Chellie Pingree tweeted her thoughts are with those who were in the LEAP building this morning, and “with the first responders, including a brave fallen firefighter, who’ve come to their aid. I’m monitoring the tragedy in Farmington + hoping for a speedy recovery for the injured.”

During an early-afternoon new conference, Franklin County Sheriff Scott R. Nichols said the loss of a Farmington firefighter and the number of others injured is a loss that is going to be a struggle for the people of Farmington to overcome.

“It was just total devastation. I’ve never seen destruction like this in my career,” he said. Nichols, who served a tour in Afghanistan, said “I’ve never seen anything like this before in my life.”

The United Way of Farmington announced the formation of a fund to aid the victims.