The team of firefighters battling the blaze had expanded to 75 by the afternoon as the battle to extinguish the blaze continued. One of the firefighting team was taken to hospital during the morning after sustaining a hand injury.
The fire broke out early Wednesday morning in the institute's architecture school on Östermalmsgatan in central Stockholm with the roof of the main lecture hall quickly filling with smoke.
Firefighters battled throughout the day to bring the blaze under control and prevent it spreading to other parts of the university's buildings and there are fears that there is a risk of a building collapse.
"It is a building which is difficult to put out as there are large halls," said Åsa Dehlin at the Stockholm fire service.
Large amounts of smoke were reported in the vicinity of KTH which is located in the Östermalm area of central Stockholm. Traffic was diverted around the location during the day.
Stockholm's fire service reported that it had no information regarding the smoke and whether it could contain any poisonous substances but advised local residents to keep windows and doors closed as a precautionary measure.
There are currently no details on whether anyone has been injured in the fire nor how it started. The affected buildings have been evacuated of staff and students.
Around 600 students and 130 members of staff are affected by the fire at the School of Architecture. The school will remain closed on Wednesday and KTH are as yet unable to say how the immediate future will develop.
"We are going to have a meeting at 2pm and at the earliest 4pm will we be able to give details of the evacuation," said Peter Larsson at KTH.
In response to question as to what would happen to the students soon scheduled to graduate if their work had been destroyed in the fire, Leif Brodersen at the school replied:
"That we have to discuss, there are a few months remaining. But we follow all the examination work and the events of today have to be taken into account. Our goal is that students should not be affected."
The architecture school is part of the Royal Institute of Technology, which is one of Sweden's top seats of learning.
KTH was placed fourth in a recent ranking of Swedish colleges and universities. Astronaut Christer Fugelsang, actor Dolph Lundgren and financier Ivar Krueger are among some of its more celebrated alumni.