Mexico's federal Health Department said Friday night that a statement it issued earlier in the day listing a death of a person injured by last week's explosion at the headquarters of the country's state-owned oil company did not mean the disaster's death toll had risen from 37.

The earlier statement by the agency listed a lone fatality, appearing to indicate a rise to 38 deaths.

But the department clarified later on its Twitter account that the death included in the report represented a victim who had died Monday and had been included in the death count released previously. It gave no reason for the confusion.

The report said 19 people remain hospitalized, two of them in critical condition. The Jan. 31 blast at one of the buildings at the Petroleos Mexicanos headquarters complex in Mexico City also injured 120 people.

Executives at Pemex have said a water-heating system may have leaked methane gas into a tunnel beneath the headquarters for more than seven months. They say the blast could have been set off by a maintenance crew's improvised lighting system.