But the hospital, the state-run All-India Institute of Medical Sciences, said it was conducting an in-house inquiry into the trials, which started in the beginning of 2006 and are ongoing.
"All the studies had undergone scientific scrutiny and had all the required regulatory and ethical approvals," the hospital said in a statement, according to the Press Trust of India news agency.
The institute said the infants died because they had "high-risk and serious disease conditions," the report said.
The hospital denied that the children in the trials came solely from poor families, a concern raised by a non-profit group that had sought information about the trials through a freedom-of-information request.
"There was no question of targeting any socioeconomic group selectively," the hospital statement said.
The hospital said more details would be provided after it completed the inquiry into the trials, which included drugs marketed by the US arm of Swiss-based Novartis and by US-based Shire Human Genetic Therapies.
Some 4,142 babies admitted to the hospital have been in clinical trials since January 1, 2006, more than half of them under the age of one, said the Uday Foundation for Congenital Defects and Rare Blood Groups, which filed the request for information.
The non-profit's founder Rahul Verma said the group hoped to publicise the need for better regulation of India's booming outsourced clinical trial business, estimated at about 120 million dollars last year.
India has become a popular destination for clinical research because of its huge population, varied demographic profile and low costs. Trials here cost 40 to 60 percent of what they would in developed countries.
Consulting firm Ernst & Young has said the outsourced clinical research market in India, which is growing at 25 percent annually, could reach two billion dollars by 2010.