Contaminants were found in Moderna Inc’s COVID-19 vaccines at a large-scale vaccination centre in Japan’s Okinawa prefecture, suspending inoculations, public broadcaster NHK reported on Sunday.

The Okinawa vaccines are from different Moderna lots already suspended by the Japanese government due to reports of contamination, NHK said.

Black substances were spotted in syringes and a vial, while pink substances were found in a different syringe filled with vaccine at the Okinawa centre, NHK said.

Takeda Pharmaceutical Co, the domestic distributor of the Moderna vaccines, is expected to investigate the possibility of contamination during production and hold talks with Japan’s health ministry, the broadcaster said.

Japan halted the use of 1.63 million Moderna doses, shipped to 863 vaccination centres nationwide, more than a week after Takeda received reports of contaminants in some vials.

The contaminant found is suspected to be a metallic powder, Japanese public broadcaster NHK reported, citing sources at the health ministry.

The report cited the ministry as telling NHK that the particulate matter reacted to magnet and was therefore suspected to be a metal. Moderna has described it as “particulate matter” that did not pose a safety or efficacy issue.

The ministry said on Saturday that two people died after receiving Moderna’s vaccine shots that were among lots later suspended following the discovery of contaminants.

Each had a shot from one of three manufacturing lots suspended on Thursday. The causes of death are being investigated.

Japan is battling its worst wave of infections, driven by the Delta variant, with new daily infections exceeding 25,000 this month for the first time.

The country has inoculated 54% of its population with at least one dose and fully vaccinated 43%, according to a Reuters vaccine tracker.