"At 3:24 p.m. (0724 GMT) on Jan. 24, a fire broke out on the below-ground level at a store... in Xinyu, Jiangxi," the country's state broadcaster CCTV reported.
"Up until now, the accident has resulted in the death of 39 people, injuries to nine people, and others are still trapped," state broadcaster CCTV reported just after 8:00 p.m. local time (1200 GMT).
The report did not specify a precise cause of the fire, or how many people were still in danger.
Chinese President Xi Jinping called for "resolute containment" of deadly accidents in the country, in a statement made after the fire.
Xi "issued important instructions... requiring resolute containment of the frequent occurrence of various safety accidents to ensure the security of people's lives and property and overall social stability", CCTV reported.
Video footage released by CCTV of the scene showed several fire trucks and other emergency response vehicles lined up across the street from a row of businesses.
State-backed outlet The Global Times posted a statement by an "emergency command" in the city, which had been set up by local officials after the fire broke out.
"At present, on-site search and rescue work is still ongoing, and the cause of the accident is also being investigated," the statement said.
Footage from the scene shared on social media by government-run outlet The Paper showed huge clouds of smoke billowing into the sky as crowds of people looked on from a distance.
Emergency response vehicles could be seen nearby as security staff told people not to go any nearer.
Fires and other deadly accidents are common in China due to lax safety standards and poor enforcement of regulations.
Wednesday's incident comes just five days after a late-evening blaze at a school in central China's Henan province killed 13.
In November, 26 people died and dozens were sent to hospital after a fire at a coal company office in northern China's Shanxi province.
The month before, an explosion at a barbecue restaurant in northwestern China left 31 dead and prompted official pledges of a nationwide campaign to promote workplace safety.
In April, a hospital fire in Beijing killed 29 people and forced desperate survivors to jump out of windows to escape.