Officials said the Telecommunication department was working to restore the telephone lines.
"The repair work is being conducted on a war footing. It is expected that the helpline service would resume at the earliest," they said.
Delhi government had launched the 24-hour helpline a month ago to help women in distress following massive public protest in the wake of the December 16 gang-rape incident.
The helpline operates from Chief Minister Sheila Dikshit's office in Delhi Secretariat.