WASHINGTON — The Biden administration said Friday that it did not know that a Baltimore factory had discarded millions of possibly contaminated doses of AstraZeneca’s coronavirus vaccine when President Biden last month released the company to ship vaccines manufactured there to Mexico and Canada.

Canadian and Mexican officials said on Friday that they had assurances from AstraZeneca that the millions of doses they received were safe. Some of the doses have been distributed to the public in both countries, the officials said.