A fire broke out in a staff office at the Singapore Polytechnic (SP) on Tuesday night.
There were no reported casualties with all staff accounted for.
The fire erupted at Teaching Block 2, Level 5 at around 7.25pm.
Students attending class in nearby buildings saw clouds of grey smoke rising from the neighbouring block.
"I saw smoke during class, at around 8.30pm," said Ms Cindy Lun, 36, a student at the school.
"The whole class took a look outside and wanted to call the firefighters. I think my mates did in the end."
Photographs of the fire filled social media pages as word spread.
The fire was put under control within an hour after the Singapore Civil Defence Force (SCDF) was called to the scene at 7.35pm.
It is currently investigating the cause of the fire.
"Singapore Polytechnic classes will not be affected by the incident and will continue as scheduled tomorrow at different locations," said a spokesman for the school on Tuesday night.
In July last year, another fire broke out at one of SP's foodcourts in the afternoon. That fire was put out by the SCDF in 10 minutes and no one was injured.