“We don’t know what caused the fire but it has been extinguished,” the head of North Sumatra’s disaster agency Riadil Lubis told AFP, adding that at least three children were among the victims.
Pictures from the scene showed blackened corpses lying on top of each other, while TV footage showed plumes of black smoke billowing from the home in the town of Binjai in North Sumatra.
“When I was about to go out Friday prayers there was a loud explosion,” said local resident Budi Zulkifli.
“Most likely they brought the kids to work,” Irwan Syahri, head Langkat disaster mitigation agency, told Metro TV.
He added that the victims “were all badly burned and hard to recognize”.
Deadly fires are not uncommon in Indonesia due to poor safety standards that are routinely flouted.
In 2017, at least 46 people were killed and dozens more injured in a blaze that tore through a fireworks factory outside Jakarta.
Seventeen people were killed when a fire ripped through a karaoke bar on Sulawesi island in 2015 and, in 2009, a fire killed 20 people at a karaoke bar in Medan, on Sumatra island.