BEIJING, March 30 -- A task force established by the Chinese government has pledged thorough investigation into and stern punishment for those involved in the scandal where millions of dollars worth of improperly stored vaccines were sold to patients nationwide.

The cross-departmental working group, led by Bi Jingquan, head of the China Food and Drug Administration, convened its first plenary session Tuesday to set the tune for the investigation.

The group was set up on Monday and headed to Shandong Province the same evening.

Anyone who tries to conceal facts or provide fake information to hinder the investigation will be harshly punished, the task force said at Tuesday's meeting, adding the scandal has exposed long-standing loopholes in the vaccine distribution system.

Officials found guilty of negligence should be held accountable, said the group, which consists of officials from departments such as the National Health and Family Planning Commission, the Ministry of Public Security, the Ministry of Supervision, and the Supreme People's Procuratorate.

The working group said progress of the its investigation, including scientific assessment of the effectiveness of and risks posed by the vaccines used in the case, will be release timely, in response to public anxiety.

Preliminary investigation shows that improperly stored vaccines worth 310 million yuan (48 million U.S. dollars) have been sold in more than 20 provinces since 2011.

Twenty-nine pharmaceutical companies have been implicated in selling the vaccines, and 16 vaccination institutions are suspected of buying them.

More than 130 people have been questioned and 69 criminal cases have been filed nationwide.