New Delhi, July 23 -- A day after a 40-year-old woman and her two daughters, aged eight and 12, died in a fire at their third-floor flat in BK Dutt Colony near Lodhi Colony in south Delhi, police on Wednesday said they had registered a case of death by negligence and were trying to reconstruct the sequence of events and ascertain the exact cause of the blaze.

The first information report (FIR) was registered against unknown persons under Sections 106 (causing death by negligence) and 287 (negligent conduct with respect to fire or combustible matter) of the Bharatiya Nyaya Sanhita, a senior police officer said.

"Although the victims' family members have said they do not suspect foul play, we still want to establish how and where the fire...