The Mundka building which was ravaged by a fire that claimed 27 lives had a single entry and exit point, which could explain the reason for the high number of casualties, a senior fire department officer said on Saturday.

The building also did not have a no-objection certificate (NOC) from the fire department, the officer added.

The fire started from the first floor of the building that houses the office of a CCTV camera and router manufacturing and assembling company on Friday.

The owners of the company, Harish Goel and his brother Varun Goel, who were detained earlier, have been arrested, Deputy Commissioner of Police (Outer) Sameer Sharma said. The building owner has been booked as well.

In videos that emerged on social media, people could be heard crying for help while others were seen jumping from the building in a desperate attempt to escape the flames.

"The rescue operation is over. The building had a single escape route which is the reason for so many casualties," said Atul Garg, Director, Delhi Fire Service.

Garg said they recovered some more charred remains on Saturday morning and the death told could rise up to 30. He said it was difficult to identify whether the remains were of one person or more.

According to the officials, there was only one narrow staircase for entry and exit in the building which made the escape difficult.

Twenty-nine people are reported to be missing.