Health officials have warned that the country's reported 424,637 cases - making them sixth globally - is not an accurate account of the coronavirus situation, due to shortages of testing and underreporting of the virus.
A letter calling for López-Gatell's "immediate" resignation bore the names of 10 state governors, all from opposition parties, was made public Friday, but later one of those governors said he had not approved the letter and distanced himself from it.
As Mexico increasingly becomes a hot spot, President Andres Manuel Lopez Obrador has largely focused on reactivating the economy over enacting strict lockdowns.
The government was slow to decentralize testing sites, preventing private companies and states from providing their own testing. Thousands of new cases have popped up in private medical centers, which are not being reported in the federal system, a report by Reuters showed in mid-June. Deputy Health Minister Hugo Lopez-Gatell, who's leading the country's response on the virus, has acknowledged that while actual cases are much higher than official counts, the Health Ministry's testing strategy is effective in tracking outbreaks.
The semi-autonomous region reported more than 100 new cases as of Saturday - among the population of 7.5 million. Only the US and Brazil have higher fatality numbers.
The letter blamed the administration of President Andrés Manuel López Obrador for "an erratic handling of the epidemic and a lack of efficient response" that simultaneously boosted Mexico's death toll to the third-highest in the world while suffering an 18.9% drop in economic activity in the second quarter compared to the same period previous year.