Mexico posted a record daily tally of coronavirus infections on Thursday, as 6,741 cases carried the overall figure to 238,511, according to the health ministry.
The new figure pushed Mexico past Iran to 10th place among nations with the largest number of cases, a Reuters tally showed.
Mexico also recorded 679 more deaths, for a toll of 29,189 since the pandemic reached the country in late February.
Deputy Health Minister Hugo Lopez-Gatell said authorities had begun examining records for causes of death linked to COVID-19, the respiratory illness caused by the virus.
The official death toll could climb once such cases were identified, he told a news conference.
Lopez-Gatell said he stood by recent comments to the Washington Post about deaths in Mexico City, which has been hit hard by the pandemic.
He had told the newspaper that actual deaths in the capital could outnumber those reported by a factor of three.
The government has often said the real number of infected people is probably significantly higher than the tally of confirmed cases.