© AFPMore than 70 miners were also injured in the incident at the Zemestan-Yurt mine
An official in the Golestan provincial government, Reza Morovati, said seven more bodies had been recovered from the Zemestan-Yurt mine, near Azadshahr.
Efforts to remove rubble and search for other bodies were continuing, he added.
The blast occurred when methane gas that had accumulated inside a tunnel was ignited, causing it to collapse.
On Sunday, President Hassan Rouhani faced a protest from angry miners and the families of victims when he visited the site.
People jumped and banged on the car carrying Mr Rouhani.
"Why is there no safety at the mine? Why does no one care?" shouted a spokesman for the miners, in a video shared on social media.
"Last year, we gathered in front of the governor's office together with our wives because we were unpaid for 14 months. And you, the president, didn't even notice."
Earlier, Mr Rouhani had declared that anyone found at fault over the accident would be "found and dealt with accordingly, without any exceptions".
The mine, which employed more than 500 workers, will stay shut for six months while an investigation is carried out.
Sunday's protest took place less than two weeks before an election in which Mr Rouhani is standing for a second term.
His conservative rivals for the presidency have accused him of failing to revive Iran's economy following the country's landmark nuclear deal with world powers.
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