Updated at 1:15 a.m.: Chelmsford Fire Chief Michael Curran told Patch that firefighters will remain on scene at the Princeton Street fire throughout the night and will continue into Thursday morning.
The fire was originally called in as a brush fire, but when the first engine company arrived they determined the flames were indeed coming from the brick building.
There was no electricity connected to the building, and when firefighters arrived they saw an "X" hanging on the side of the building. That sign indicates that firefighters are not to enter the building under any circumstance as it would create a dangerous situation.
As a result, firefighters sprayed the flames from above with ladder towers and methodically worked around the building in an effort to put out the blaze.
"It will be a long night ahead because there will be hot spots all night," said Curran. "We'll have to get a piece of equipment in here (Thursday) morning to start tearing it down and wetting it down as it comes apart."
Curran said the fire is still under investigation and it is not clear at this time if it was intentionally set. The Chelmsford Fire Chief also added that there were no injuries reported. Because the majority of the flames were rising from the outside of the building and not the interior, Curran said it's likely there was no one hurt in the fire.
Original Story: A fire broke out at a vacant structure on Princeton Street just before 11 p.m. on Wednesday night.
It's currently unclear what started the fire, but after midnight firefighters were still working extensively on the second floor of the building.
According to witnesses on scene, the building is an unoccupied part of the University of Massachusetts Lowell West Campus.
Some flames remain active on multiple sides of the building while smoke continues to pour from the structure.
Check back with Chelmsford Patch for more details as they become available.