Mainland health authorities do not believe hepatitis B vaccinations played a role in the deaths of 17 infants.
But Yu Jingjin, a department chief at the National Health and Family Planning Commission, said they would wait for the final autopsy reports before reaching a conclusive decision.
Concerns over the safety of hepatitis B vaccinations arose after four children died within 24 hours of receiving a shot made by Shenzhen-based Biokangtai Biological Products, all between December 13-19.
But Yu said that only in a fifth, non-fatal case, was the vaccination possibly a concern. An infant may have had an allergic reaction after receiving a shot, but recovered in hospital, according to a transcript of a press conference posted on the commission's website. Many of the other suspected cases reported by parents following the news of the initial deaths were not related to the vaccination, it said.
Experts had ruled out a link in nine of 13 of those cases brought forward. The remaining cases did not appear tied to the vaccination, but again, authorities would wait for the final autopsy reports, Yu said. The fatalities occurred in 18 different counties in nine provinces and the vaccines came from different batches, except in the instance of two infants in Hunan , who received doses from the same batch.
There was no consistent cause of death across all cases - severe pneumonia, kidney failure, infantile diarrhoea and congenital heart disease were all listed, and these are common killers of children under five on the mainland.
Health authorities ordered a ban on vaccines produced by Biokangtai, which specialises in hepatitis B vaccines, after reports emerged that seven infants died after receiving shots, in Sichuan , Guangdong and Hunan.
It then failed to meet new guidelines for good manufacturing practices that came into effect with the new year. Two other major suppliers, Beijing Tiantan Biological Products and Dalian Hissen Biopharm, were also forced to halt production after they failed to obtain the certificates.
Li Guoqing, of the China Food and Drug Administration, said no problems had been found with Biokangtai vaccines.
The investigation was conducted by four experts engaged in vaccine certification and good manufacturing practice inspection. It had looked at possible contamination and other scenarios that might affect product quality, Li told reporters.
The National Institute for Food and Drug Control inspected 956 vaccines from two batches collected in Hengshan county, Hanshou county and Changning in Hunan, and they passed all tests. The institute had also conducted spot checks of 16 batches of hepatitis B vaccine from four manufacturers, including six batches from Biokangtai, in 2011, and 24 batches from four manufacturers, including four batches from Biokangtai, a year later - and all met the national standard.
The World Health Organisation's China wing said in a statement last night there was "no evidence that the quality of the vaccine has caused these … events".
But the reports have shaken the confidence of parents. The Chinese Centre for Disease Control and Prevention had found hepatitis B vaccinations had dropped 30 per cent in 10 provinces.