In response to the health secretary's claims, a think tank, Mexicans Against Corruption and Impunity (MACCIH), started an investigation into the number of death certificates versus the number of reported deaths from coronavirus.
The Latin American country reported a record 8,458 Covid-19 associated deaths in 24 hours to surpass Britain's 46,119 death toll.
The U.S. has reported the most cases in the world, with 4.6 million, and 154,000 deaths.
USA coronavirus deaths rose by over 25,000 in July and cases doubled in 19 states during the month, according to a Reuters tally, dealing a crushing blow to hopes of quickly reopening the economy. A total of 284,847 people have recovered from the disease.
A man is tested for Covid-19 in Mexico.
Mexico racked up a record number of new confirmed coronavirus infections on Saturday, registering more than 9,000 daily cases for the first time and passing the previous peak for the second day running, official data showed. He has denied charges of hiding members and underreporting gatherings to avoid broader quarantines.
Latin America is now one of the pandemic's global hotspots. All were tested, their movements monitored with electronic wristbands and required to be quarantined before and after.
The country's Civil Aviation Ministry delayed resumption of worldwide flights by another month until August 31.
Hurricane Isaias' imminent arrival has forced the closure of some outdoor testing sites in the country. The country is not permitting general travel to and from the countries, which include the United States and Brazil.
On Friday, the head of the World Health Organization predicted the effects of the pandemic will be felt for "decades to come".