The Fredericton Region Museum has reopened after being shut down because of oil fumes in the building.
The smell of gas is gone, but its origin remains a mystery.
"No one knows where it comes from, the city is trying to determine that," said Fred White, treasurer of the York-Sunbury Historical Society board.
The museum at Officers' Square was closed to the public starting April 22, initially because of flooding.
White said employees noticed an oil smell on May 3 and called city officials, who brought in professionals to investigate.
The museum was given the all clear on Tuesday to reopen, and resumed interviewing summer students and retrieving artifacts that were moved to safety before the flood.
Neil Thomas, a water and sewer engineer with the City of Fredericton, said an engineering consulting firm has been brought in to look for the source of the oil smell.
A survey was done of the storm-sewer network around the building and a geophysical survey was done of the area around the museum to check for buried oil tanks. Neither shed light on the fumes.
"These are all non-intrusive methods of investigation to give us possible leads to next steps," Thomas said.
The city doesn't have all the data from the consultant yet, but Thomas said a possible next step would be to inspect the soil around the foundation of the building.
The spring flood brought water into a small stone cellar attached to the museum. That was where the gas odour was detected, Thomas said.
Fans are still running downstairs, but there is no longer a smell of oil. The city's building services department is also working on improving ventilation.
While repairs wrap up and the museum prepares for the summer season, the investigation of where the oil could have come from continues.
The museum has been heated electrically since the 1960s.
"The last time this building was heated with oil was approximately 60 years ago," Thomas said.
"We are a little bit perplexed as to where the source may have come from."
Thomas estimated the cost of the investigation will end up in the "low tens of thousands of dollars."