Brazil’s health regulator temporarily blocked more than 12 million doses of Sinovac Biotech’s COVID-19 vaccine on Sept. 4.

Anvisa took regulatory action after receiving a complaint from Sao Paulo’s Butantan Institute biomedical center. The center, which helps the Chinese firm manufacture locally, accused the Asian pharmaceutical company of unlawfully producing several vaccine batches in an unauthorized plant.

“[The manufacturing unit] was not inspected and was not approved by Anvisa in the authorization of emergency use of the mentioned vaccine,” the regulator said according to Reuters.

The regulator stopped a total of 25 non-compliant batches to avoid exposing the population to “possible imminent risk.” The same production facility was expected to deliver a further 17 batches (9 million shots).

Plant operation will remain suspended for a total of 90 days, allowing Anvisa representatives to inspect and investigate the facility’s compliance. Neither Anvisa nor Butantan revealed exactly where the plant is located.

Brazil recently experienced a reduced rate of daily infection since peaking in late June. World Health Organization data confirmed 152,154 COVID-19 cases, representing a decreased rate of 13.45 percent as of Aug. 30. The South American country recorded 21,804 new infections and 692 fatalities on Sept. 4.

The Sinovac vaccine is widely administered in low- and middle-income countries. These shots are found to be less effective than those made by competitors Pfizer, Moderna, and Russia’s Sputnik according to Bloomberg.

Authorities were urged to begin administering booster shots due to growing Sinovac vaccine-efficiency concerns, especially when it comes to the Delta variant according to the Associated Press.

“I cannot go out like before and I am still afraid of all of this,” Brazilian patient Diana dos Santos, 71, said after receiving both Sinovac vaccine doses. “I will feel safer [with a booster.]”