In March 1902, nineteen Indian villagers from Mulkowal in Punjab (inoculated from a single bottle of vaccine) died of tetanus, whilst the other 88 villagers were well. Evidence pointed to the contamination of one bottle - 53N. The procedure for sterilisation at the Parel lab had been changed from carbolic acid to sterilisation using heating, a process that had been used at the Pasteur Institute safely for two years but was new in the British Empire.