The gutted weapons include an INSAS assault rifle and two self loading rifles and the bullets were of these firearms, city superintendent of police Shivdeep W Lande said.
Rana is out of the city on a week's leave.
"The fire broke out at the SSP residence around 1.30 AM. It seems electric short-circuit triggered it. Though it was controlled in an hour, the weapons and bullets were burnt by that time," Lande said.
Though the fire broke out in the early hours, the constables informed about it in the morning.
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Fire brigade was also not informed and the flames were doused by the constables themselves.
"The constables were afraid of telling about the incident as official weapons were lost in it. It is a serious matter and action will be taken against those who are found responsible for it," Lande said.
A probe into the incident has begun and prima facie it appears that the short circuit happened in an electric heater in which food was prepared, he added.