A fire broke out Tuesday morning at a room in the Prime Minister's Office (PMO) in the South Block here, officials said.
There was no report of injury or damage to property, a PMO official said.
"There was a short circuit in a computer UPS in the PMO's room in South Block, which triggered off a smoke detector. The fire alarm went off and fire service reached the spot," said the official.
Delhi Police, who are now investigating the incident, said: "The cause of fire is suspicious as the room was locked."
Delhi Fire Service said the fire was reported at 6.48 a.m. and was doused at 7.35 a.m. "Ten fire tenders were rushed to the spot," said a fire service official.
The fire was reported in Room number 60 in South Block, which belongs to a joint secretary in the PMO.