Moderna vaccines are being prepared for use at a U.S. military vaccination center at Camp Foster on April 28, 2021 in Ginowan, Japan.

Carl Hof | Getty Images

Japan’s Ministry of Health, Labor and Social Welfare suspended the use of more than 1.6 million doses of Moderna’s Covid-19 vaccine on Thursday after reports of contaminated vials at multiple vaccination sites there.

Takeda Pharmaceuticals, which sells the vaccine in Japan for Moderna, said it notified the ministry after multiple vaccination sites reported an unspecified foreign object found in a specified lot.

“We asked Moderna, the owner and manufacturer of the product, to conduct a thorough investigation to determine the exact cause of the problem,” Takeda said in a statement.

Takeda also said he was not aware of any “significant safety concerns” related to the contaminated cans.

Moderna said it had been informed of the problem and would investigate it.

“The company is investigating the reports and remains committed to working expeditiously with its partner Takeda and regulators to address this,” Moderna wrote in a statement.

Japan’s chief cabinet secretary Katsunobu Kato told reporters Thursday that contaminated doses were administered to an unknown number of Japanese people, despite no reports of side effects, according to the New York Times.

All contaminated vials were made at production sites in Spain. It is still unclear whether other countries besides Japan are affected, although the European Medicines Agency has announced that it will also investigate the problem.

“The EMA is investigating the matter and has asked the marketing authorization holder to provide information on possible effects on batches shipped to the EU as well as details of ongoing research into the cause,” the agency said in a statement to Reuters.