Japanese officials halted inoculations with Moderna’s COVID-19 vaccine at a large-scale vaccination center in Okinawa after contaminants were found in some lots.

The Japanese health ministry said two people died after receiving possibly contaminated vaccine shots. A black substance was reportedly discovered in a syringe and a vial, and pink substances were found in a syringe filled with vaccine.

In a separate contamination incident, Japan last week halted the use of 1.63 million Moderna doses distributed to vaccination centers due to possible contamination.