An unidentified suspect used concrete cleaner and a cigarette lighter to start a small fire in the Free Expression Tunnel early Friday morning, University spokesman Keith Nichols told The News and Observer.

Fifteen gallons of the chemical, which was stored near the tunnel, was used to start the fire, which began a few moments before 6:30 a.m. and was declared extinguished less than an hour later, said a report in the News and Observer.

While the fire could not technically be classified as arson, as the fire was not set in an occupied dwelling, Campus Police told the News and Observer that the fire appeared to have been set on purpose.

Campus safety officials who responded to the scene of the fire initially attempted to use a water-based extinguisher, which was ineffective on the chemical-based fire. Firefighters from Campus Fire Prevention and Raleigh Fire Department then decided to let the fire burn itself out, Nichols said to the News and Observer.

The fire caused very little damage to the tunnel but was cause for worry for several different railroad companies whose trains run on the tracks over the tunnel. Norfolk Southern kept all trains off the tracks while the fire was burning, and passenger train company Amtrak was forced to delay the departure of its Piedmont train, which runs from Raleigh to Charlotte, by 10 minutes because of the fire, Amtrak spokesman Cliff Black told The News and Observer.

It is unclear whether the fire will further delay the re-opening of the tunnel. Campus Facilities division was unavailable for comment on the issue.