HALIFAX -- The Saint John Fire Department is investigating an overnight fire that damaged a building at the Fort La Tour National Historic Site in Saint John, N.B.

"We just, we're devastated. There's no words. It's sad, it's disappointing, we've been working years for this," said Beth Kelly Hatt, chair of the Fort La Tour Development.

According to Platoon Chief Ed Moyer with the Saint John Fire Department, crews responded to the fire just after 2:30 a.m. on Wednesday.

Officials say the damage to the building was contained to the entranceway of the fort and the smaller interpretation building where admissions would take place.

"There's substantial damage to the structure itself, to the building itself," said Platoon Chief Steve Voutour with the Saint John Fire Department. "Structurally, I believe it's sound. I believe it's going to be able to remain on scene but there is significant damage."

The fire department has deemed the fire as suspicious and the investigation is ongoing.

Fort La Tour recently underwent a $1.8 million redevelopment to add replica buildings from the 1600s and was set to reopen in about three weeks.

According to Hatt, insurance will cover a good portion of the damage. The community has also stepped up to help in any way they can.

"We've been working years for this ... and I'm blown away by the community rallying this morning and how much help we've been offered," said Hatt.

The site dates back to the 1600s and the archeological site was designated a national historic site in 1923.

In a tweet Wednesday morning, the mayor of Saint John, Don Darling, said he is deeply saddened by the news.

"This project took many years to complete," wrote Darling in a tweet. "While we're not sure of the cause, if this was set on purpose, it will have been a senseless act. Thank you to our first responders for their swift work."