MADISON, Wis. -- Madison firefighters put out a "small" fire in a wall in Grainger Hall on the University of Wisconsin-Madison campus on Monday afternoon.

Firefighters were called to the building just before noon today because of reports of smoke in the building. Crews found large room near the entrance filled with smoke and people still in the building.

Madison Fire Department spokeswoman Lori Wirth said evacuation was slow to take place, which delayed efforts to extinguish the fire.

Firefighters said that they located fire in an exterior wall of the building, near the main entrance, facing University Avenue. Wirth said that the source of the fire was difficult to determine, but the fire was put out using foam.

There was damage to an area of the wall below the front windows, she said.

Wirth said that a flood of pedestrians walking by on the sidewalk made it difficult for fire crews to do their job. Fire officials had asked all traffic to stay away from University and Park.

An investigator is at the building with UW maintenance personnel to try and determine the exact cause of the fire, Wirth said.

No one was injured. She said that damage estimates haven't yet been tallied.

Classes continue to be held at the building on Monday night.

Stay tuned to WISC-TV and Channel 3000 for continuing coverage.