Tokyo, Aug 29 (IANS): The Japanese health ministry said on Saturday that two men had died after each received two shots of Moderna Inc.'s Covid-19 vaccine, local media reported.

According to the ministry, the two men aged 30 and 38 died within days of receiving the second injection on August 22 and 15, respectively, and no foreign matter was found in either of the vials of vaccine used on the two men, the Xinhua news agency reported.

It remains unknown whether there is a causal relationship between the vaccination and their deaths, the ministry said, adding that neither of them had an underlying medical condition or a history of allergic reactions.

Japan's health ministry said Thursday that foreign substances have been found in 39 unused vials at eight vaccination sites in five prefectures. The same day, about 1.63 million doses that came from the same production line of a Spanish factory were suspended to use as a precaution.

However, more than 500,000 shots have already been administered from the potentially contaminated batches, said Taro Kono, the Japanese minister in charge of the vaccination effort.

Although the foreign substances had been confirmed since August 16, the Japanese drugmaker Takeda Pharmaceutical Co., which is in charge of the sale and distribution of the Moderna vaccine in Japan, waited until Wednesday to report the problem to the ministry.

Moderna and Takeda said in a joint statement Saturday that they were working with the health ministry to investigate the two deaths.

The two companies said that at this time, they did not find any evidence that these deaths were caused by the Moderna Covid-19 vaccine.