The investigation into an Old Town structure fire is concluded, but two main streets will be closed for part of today as clean-up crews work.

Old Town Police Deputy Chief Lee Miller said in a media release that both Main and Water Streets will remain closed for part of Monday. City officials are working to get both streets open as soon as possible, and hope to accomplish that sometime today.

The fire, that was reported just before 10:00 Saturday night, destroyed one building and left several others heavily damaged. A witness video shows how the fire spread from one building to another, due to the close proximity to each other. Miller says the State Fire Marshal's office conducted an investigation and determined that the fire started on the third floor of 274 Main Street. The damage was so extensive, however, that they were unable to determine an exact cause.