The state government of Uttar Pradesh admitted that the air supply to the apparatus is interrupted, however, said the cause of death was.
Most of the victims were newborns or patients with encephalitis.
All these deaths happened within five days in the hospital a Woman Raghav Das in the district of Gorakhpur. Thirty of them occurred in the period between Thursday and Friday, said the hospital.
Local media reported that the hospital began to panic, relatives of the children helped staff to maintain artificial respiration manually.
The representative of the municipality Anil Kumar acknowledged that the supplier was a "billing issue", but said the death could be due to "natural" reasons, as many of the patients were in serious condition.
The Minister of health of the state of Siddhartha Nath Singh also denied that the mass death caused a lack of oxygen. At the hospital, recorded 19 to 22 deaths every day for the last three years, he said. He did not specify whether it is just for children or for all.
Uttar Pradesh is one of the poorest in India. Annually from diseases, including encephalitis, where hundreds of children die.
"Tonight or tomorrow we get more oxygen tanks. We also paid supplier," - said Kumar.
In a statement the hospital said that "the pressure of oxygen was low," which required the backup cylinders. There does not specify whether this was the cause of someone's death and why so many children died just a couple of days.
Uncle of 11-year-old girl who died in hospital, said channel Hey-bi-PI: "We didn't understand what was happening. The staff told us to press the mask after each account to three. And some time we did".
The case has caused outcry in India, some called the incident a massacre, the correspondent bi-Bi-si in new Delhi Sanjoy Madjumder.
Opposition leaders gave the event a political sense and accused in the incident party "Bharatiya Janata" Prime Minister Narendra modi who is in power in Uttar Pradesh.
Representatives of the state declared the beginning of investigation, the apparatus modi tweeted that monitors the situation.