POULSBO — The fire that closed the Poulsbo Wal-Mart for more than three days was officially declared an arson Monday afternoon by the Kitsap County Fire Marshal’s Office.

“We believe it was an arson, and we’re pretty much done with our part of the investigation,” said Kitsap County Chief Fire Marshall David Lynam.

Since the incident occurred within the Poulsbo city limits, the Poulsbo Police Department is now in charge of the investigation, he said.

The store was evacuated at around 9 p.m. Thursday after employees responded to a fire in the women’s lingerie department. The fire was extinguished by the time emergency responders arrived, but the store sustained massive smoke damage.

“We were able to open our doors to our customers at 7 (a.m.),” store manger Doug Ayerst said Monday. “It’s been a long weekend.”

The exact damage total from the incident won’t be known for some time, because the lost inventory, wages and final cleanup costs must be tallied, Ayerst said. The Poulsbo Fire Department reported the initial damage estimate at $1 million.

The Poulsbo Police Department is the lead agency on the case and is treating it as a crime at this time. said PPD detective Grant Romaine.

“We’re working with the Wal-Mart loss prevention team,” he said.

That work includes examining photos from several different surveillance cameras in the store to develop a timeline for the incident, Romaine said.

“We can’t be 100 percent sure. We’re investigating it as a crime until it’s proven otherwise,” he said.

Crime or not, the cleanup was punishing.

“The entire ceiling was handwashed with a sponge,” Ayerst said. “We were able to reopen because of our wonderful team of associates who worked really, really hard.”

Throughout the weekend, store employees and outside cleaning crews removed all of the damaged inventory and restocked the shelves for Monday’s opening, he said.

“We got the food area reopened. It will probably be the end of the week before we’re fully back,” Ayerst said, explaining that several law enforcement agencies are still investigating the incident.

Wal-Mart spokeswoman Marisa Bluestone said the fire appears to be an isolated incident.

“We are happy that none of our customers and associates were injured in the fire,” Bluestone said. “We’re just happy to be open again.”

The store was thoroughly cleaned before it was reopened to both its employees and customers, she said.

Anyone with any information about the incident is encouraged to call the Poulsbo Police Department at (360) 779-3113 or the Crime Stoppers hotline at (800) 274-6313.

“Any information we can get from the public will be greatly appreciated,” Romaine said.