Four infants died after receiving routine immunisation during a government drive on the outskirts of Lucknow on Saturday.
The infants, aged nine to 12 months, died within minutes after they were injected with measles vaccine and given a dose of vitamin A in Mohanlalganj town, 25 km from here.
"It appears that the cold chain of the vaccines was disturbed during transportation. There seems to be no problem with the vaccine itself because hundreds of other children in the district have been administered the same batch of vaccine," said S.P. Ram, director general, Family Welfare, UP.
The bodies of the children have been sent for post-mortem.
The government has put the immunisation drive on hold. The programme included immunisation doses against measles, tuberculosis, hepatitis and vitamin A deficiency.
A magisterial probe has been ordered into the incident.
Under the inquiry, all vaccines administered will be tested in the laboratory.
Five members of the medical staff have also been suspended.
"Five employees including Dr K.P. Upadhaya, who was on duty but did not accompany the vehicles taking the vaccines to Mohanlalganj for the drive, an employee responsible for maintaining cold chain and three auxiliary midwife and nurse have been found guilty and placed under suspension," Ram said.
The district magistrate has ordered an ex-gratia of R50,000 to be paid to each of the affected families.