Family members of children who received a vaccine and then died or became ill want "sincere communication" with Shanxi provincial authorities, following the local government's announcement on Monday that an investigation has begun.

"I have never been contacted or interviewed by health officials or officials with the ongoing investigation until now," Yi Wenlong told China Daily on Tuesday. Yi is the father of 16-year-old Ling Ling, who has been diagnosed with acute disseminated encephalomyelitis after receiving shots for epidemic cerebrospinal meningitis in December 2006.

Shanxi Provincial government hold the press conference.

"Although I'm dissatisfied with the latest government response, I'm still longing for communication with officials to find the real cause behind my daughter's illness," said Yi, a former merchant from Hongtong county of Linfen city.

Yi's family has spent more than 1 million yuan ($150,000) to try to cure the girl, who still suffers from seizures and headaches.

The China Economic Times reported last Wednesday that problematic vaccines administered by the provincial Center for Disease Control and Prevention (CDC) had killed four children and sickened more than 70. They had been vaccinated against hepatitis B, rabies and Type-B encephalitis from 2006 to 2008.

The report cited Chen Tao'an - a whistleblower who had worked with the provincial CDC - who blamed improperly-stored vaccines for the deaths or disabilities of the children.

"I just hope my act will eventually improve the vaccine management system in our country," said Chen, 49.

The Shanxi provincial government held a press conference on Monday, admitting the provincial CDC and the vaccine producer have violated rules. However, officials reiterated that the vaccines, though once exposed to hot temperatures, were safe.

Some parents came to Taiyuan, the provincial capital city, to seek the truth behind the children's deaths and illnesses.

Wang Weifeng, father of 2-year-old Xiao Yu, who was diagnosed with the measles one week after being vaccinated against them, came to the city on Tuesday.

"Doctors told me my daughter's illness might have been caused by the vaccination. I hope the government can give us a satisfactory explanation," he said.

On March 21, Chen, along with four families whose children were sickened or died, received text messages and phone calls from unidentified people, threatening them to stop pushing authorities to investigate, or they may "lose one leg".

Yi tried to report the threat to the city's Yingze police station on Tuesday, but police officials refused to register a complaint, saying it was not within the range of the station's jurisdiction.

Several lawyers from Beijing are expected to provide legal aid to the families, an anonymous source close to the families said.