Dozens of people were killed in rebel-held territory in northeastern Myanmar on Sunday after a massive explosion at a warehouse leveled large parts of a village.

The blast occurred around noon on Sunday in Kaung Tup, a village in Shan State near the Chinese border, at a building that stored explosives for mining and quarrying, according to the Ta’ang National Liberation Army, which the controls the area. It said the incident was “accidental” and the cause was under investigation.

It did not give specifics about casualties, but local media and a rescue worker said at least 55 people had died, including children.

Footage posted on social media showed white clouds of smoke in the air followed by a massive secondary explosion. Some residents thought it was an air raid by Myanmar’s military, which rebels say has kept up attacks despite agreeing to a cease-fire in October.

“The sound was so loud that we thought an aircraft was dropping bombs,” Lway Poe Nge, who lives in Kaung Tup, said by telephone. “My house was completely destroyed.”

She said that she and her mother managed to escape because they ran out quickly from their house; but that her cousin, who lived next door, died after rubble fell on her house.

Mai Kham, a rescue worker who arrived from the neighboring town of Namkham, said that at least 55 people had died, including six children and three Chinese citizens. He said 74 people were injured. Shwe Phee Myay, a news agency in Shan State, reported a similar death toll.

“When we arrived at the village, nearly the entire village had been destroyed,” Mr. Mai Kham by telephone.

It was not immediately clear who owned the building where the explosion occurred. The Ta’ang army could not be reached for comment. Ms. Lway Poe Nge, the resident, said that many Chinese people worked there, adding that she did not know any specifics of the operation.

Sunday’s explosion occurred just three kilometers, or less than two miles, south of the Chinese border. On the Chinese side, in the city of Ruili in Yunnan Province, the authorities said that some residents had seen smoke but “it did not affect their daily lives or work.”

Unregulated mining, particularly for rare earths, has proliferated in Myanmar in recent years, as the country has become even more fragmented by a civil war, which began after the military seized power in a coup in 2021. There are now hundreds of mines near the border between Myanmar and China that dig up these minerals and ship them to China.

That is one reason, analysts say, that China has intervened in the war in Myanmar.

In 2023, the Ta’ang army was part of an alliance of rebel forces that took several key territories from the junta, including the town of Namkham.

Last October, after immense pressure from Beijing, the Ta’ang group signed a cease-fire with Myanmar’s military. It was forced to hand over key towns to the junta but balked at the request to give up others, including Namkham. Relations between China and the Ta’ang army have been tense since.

Myanmar has a long history of catastrophic mining disasters, particularly in the jade mining region of Kachin State in the north. Because mining is a profitable business for both the junta and the ethnic armed groups, worker safety regulations are rarely enforced. The owners of these errant mines are almost never punished.

Berry Wang contributed reporting from Hong Kong.