However, the threat of radiation leak has been ruled out.
While the process of identification of the victims is on, sources at BARC said that the victims could be students.
"The fire broke out in the chemical lab on the third floor of the Modular lab atthe BARC," said Director and Atomic Energy Commission Chairman Sreekumar Banerjee.
The blaze was put out by fire tenders within 45 minutes.
The cause of fire is yet to be determined by fire brigade and police.
BARC has been put on high security alert following reports of terror threats on the country's prestigious nuclear facility where a number of departmental labs and hundreds of people work on different floors of the building.
The lab is astorehouse for instruments, chemicals and gadgets required for research.
Though the seven usually work in the lab, only two students were in the lab on the fateful day.