The fire broke out in the PC building, which is a teaching block and mainly comprises research labs. However, the Microbiology Department's Virology unit was completely gutted while several samples and medical reports were destroyed.

Former Finance Minister Arun Jaitley, who is currently undergoing treatment at AIIMS, is admitted at the Intensive Care Unit (ICU) of the cardio-neuro centre, housed in a different building in the complex.

According to Atul Garg, Chief Fire Officer of Delhi Fire Services, a call regarding the fire was received at around 4.50 p.m. following which 34 fire tenders were rushed to the spot.

"The fire broke on the second floor in the PC building which does not have patients but is situated near the Emergency block. The fire was brought under control at around 6.30 p.m.," said Garg adding that no casualty was reported.

Another fire official said the exact reason behind the fire is yet to be ascertained, though initial investigation suggests a short circuit.

As panic spread among people, authorities closed some nearby buildings housing the Emergency and other facilities and shifted the patients to other wards.

"As a precautionary measure, authorities closed the Emergency department which is adjacent to the building that caught fire," a source in the hospital said, adding that B block, ward AB1, and super specialty OPD area of AIIMS have also been shut down.

"Patients were shifted to other wards from the Emergency department soon after the building caught fire," the source added.

Sources in the Fire Department said that the blaze spread to the Emergency Lab in the department of Lab Medicine, where electricity work was going on for some time and cable and wire being used were kept.