A Shenzhen-based company has come under scrutiny since it emerged that babies have been dying shortly after receiving a hepatitis vaccine made by the company. It emerged Sunday that a one-month old baby in Zhongshan died November 20, just 12 hours after receiving the vaccine, in addition to two babies in Hunan who died last week, Nandu Daily reports.

The entire product chain of Shenzhen Kangtai Biological Products Co. (BioKangtai) is being investigated after the deaths of the three babies. Another is in intensive care in Hunan’s Hanshou County. Preliminary tests showed there was no direct link between the deaths and the vaccines, according to Shenzhen Daily.

The paper has more:

Shenzhen’s drug administration said the manufacturing of BioKangtai vaccines with batch numbers C201207088 and C201207090 met production and quality standards.

The vaccines have been sold in Hunan, Guizhou and Guangdong provinces, but not in Shenzhen.

The three provinces suspended use of the two batches of vaccines after receiving a notice from China’s drug administration.

Guangdong has used 190 of the 3,600 vaccines it purchased from the batches. The provincial CDC didn’t receive any negative report

On the same day the baby in Zhongshan received the vaccination, nine others received it without any adverse reaction.

BioKangtai was founded in July 1988 in Nanshan District and is the largest manufacturer of hepatitis B vaccines in China, taking around 60 percent of the domestic market.