The foreign substances have been confirmed since Aug. 16 at eight vaccination sites in five prefectures — Ibaraki, Saitama, Tokyo, Gifu and Aichi. They were found in a total of 39 vials.

Takeda reported them to the ministry on Wednesday.

The composition of the foreign matter, a few millimeters in size, has not been determined.

The „small black materials“ reported to the ministry could be metallic fragments, one of its senior officials said.