A fire in a hospital in Kolkata, India killed at least 73 people on Friday and the owners of the hospital have been arrested, according to the Times of India newspaper.

The fire was detected at 3:30 a.m. Friday. It spread fast from the basement of the 7-story hospital and unfolded over many hours, according to the report.

Firefighters took an hour to reach the scene. Initially they did not have proper equipment, had no masks and only rickety manual lifts, local media reported.

Among the casualties were three hospital staff, the Times of India reports. Reuters reports at least two of the dead were children.

Six directors of the private hospital operated by AMRI, a prominent chain of clinics in the city, surrendered to police, according to the Times of India.

The Chief Minister and Health Minister cancelled the operating license for the AMRI hospital, Reuters reported.