The store belonging to minimarket chain Alfamart suddenly collapsed at around 5:15 p.m. local time. Police said 15 people including six store employees and nine customers were inside the building when the incident occurred based on accounts from eyewitnesses.
"Eight survivors have been rescued from the scene and they are now being treated at several hospitals," South Kalimantan Police spokesman Chief Comr. Mochamad Rifa'i told Antara news agency.
The search for other victims using an excavator continued on Monday night.
The store is located on Jalan Ahmad Yani in the town of Banjar, about 40 kilometers from the provincial capital, Banjarmasin.
Witnesses said they heard loud cracking sounds before the building instantly collapsed to the ground within seconds.
Sumber Alfaria Trijaya, the company that owns the minimarket chain, expressed concern and offered condolence to the families of the victims.
"Alfamart will cover all medical costs and provide financial compensation for the victims," Solihin, the company's Corporate Affairs Director, said in Jakarta.