LEWISTON — Yellow light from Rachel Desgrosseilliers’ waning flashlight played across charred wooden beams Monday, then washed over unwound skeins of yarn strewn across the floor.

The stench from Sunday’s fire at the former Camden Yarns Mill at 1 Beech St. saturated the hair and clothing of Museum L-A’s executive director.

As she surveyed the damage wreaked on the future home of her beloved Museum L-A, Desgrosseilliers’ expression was that of a mother in mourning.

When the 15-year-old Museum L-A was outgrowing its space in the former Bates Mill, its board of directors took ownership of the Camden Yarns Mill building and grounds just south of Simard-Payne Memorial Park in 2009 from the Miller family, which had owned the property since the 1930s.

Since then, the vacant building on the banks of the Androscoggin River has suffered one setback after another.

Three years ago, thieves stole hundreds of antique gears Desgrosseilliers had collected in hopes of using them to raise money for the new site of the museum.

Two years ago, vandals scavenged $17,000 worth of copper from the building, she said.

Around that time, squatters had broken into the place through an elevator shaft door and left their sleeping bags and clothes, she said. She had later secured the door, leaving their belongings outside the door, thinking “at least, I hope, we helped them,” having provided temporary shelter.

On Monday, more evidence of squatters — a jacket and an empty beer can — was found on the first floor near a rear door. A board nailed over the door had been sawed in half. Scorch marks on the floor and wall in that area suggested squatters had lit a fire for warmth.

Standing in the dark amid the debris, Desgrosseilliers guessed her group would have to raise even more money to cover the cost of damage.

But Desgrosseilliers said she was determined as ever to see the museum meet its mission to pay homage to the Twin Cities’ history of industry and to those workers who had flocked to its mills seeking a better life.

“We’re not giving up now,” she said. “We’ve worked too hard.”

Lewiston Fire Inspector Ryan Coleman said Monday the cause of the fire remains undetermined. All elements, except for a human one, have been ruled out, he said.

Damage from the three-alarm fire, which likely smoldered for days before wisps of smoke were spotted and reported, was confined to a small area in the basement.

The smoke was so thick inside firefighters had to breath compressed air through masks, Coleman said. No injuries were reported.

He said engineers should assess the structural integrity of the building, especially where the damage occurred, charring thick floor planks.

Desgrosseilliers said once she receives Coleman’s report, she will meet with the museum’s board and then create a plan for moving forward.

“What do we do now?” will be the question, she said.

As potentially destructive as the fire was, she said the vandalism of the collected artifacts, including barrels of yarn, was perhaps the most disheartening sight Monday inside the old mill.

Blankets, woven at the mill from the salvaged threads of ancient rags, were ripped from their boxes and protective plastic bags. Vandals damaged and dirtied the unique weavings.

“This here,” she said, pointing. “There’s no reason for this. This is not good, This is not right.”

There was no insurance to cover the property damage, she said. The only quote offered was far more than the budget could cover, so they carried only liability insurance, she said.

She had last been inside the building about a month ago. She had been looking for someone to secure a window panel that had been sawed off at the bottom.

“But it’s not easy to find volunteers today,” she said.

A man who would check regularly on the building retired a few months ago, she said.

Despite the thefts, vandalism and fire, Desgrosseilliers remains determined.

“A couple of times I’ve said, ‘Geez, we’re working so hard to do this.”

She bounced back each time, thinking of the elderly folks who appreciate the museum’s efforts to retain their legacy.

She also sees young people who are able to see and touch history on visits to the museum.

“They are learning about who we were are as a people,” she said. “There is no question in my mind that this has to happen because the stories of who we are have to be saved and kept.”