Beijing, China (CNN) -- The death toll from an explosion at a northeastern China coal mine rose to 104 Monday morning, according to state-run media.



Another four workers were still trapped underground in the mine shaft as of 7:20 a.m. (6:20 p.m. ET Sunday), the Xinhua news agency said. A buildup of toxic gases was hampering rescue efforts, according to CCTV.



Sixty miners remained hospitalized Monday for injuries ranging from carbon monoxide poisoning to burns, CCTV reported. Of those, six had sustained severe burns that left them in critical condition.



About 530 miners were working in the mine when the blast occurred at about 2:30 a.m. Saturday (1:30 p.m. ET Friday). The Heilongjiang Longmei's Xinxing mine is operated by the Hegang company.



A preliminary investigation indicates the blast was a gas explosion, Xinhua reported.
What was was hampering rescue efforts? What was hampering rescue efforts? What were the miners in the hospital for? What kind of workers were trapped? How many workers are still trapped? What is the Death toll doing? What is the number of miners hospitalized? How many miners  were hospitalized? Who is still trapped?
A buildup of toxic gases A buildup of toxic gases injuries ranging from carbon monoxide poisoning to burns, miners four rose to 104 Sixty Sixty four workers
question: What was was hampering rescue efforts?, answer: A buildup of toxic gases | question: What was hampering rescue efforts?, answer: A buildup of toxic gases | question: What were the miners in the hospital for?, answer: injuries ranging from carbon monoxide poisoning to burns, | question: What kind of workers were trapped?, answer: miners | question: How many workers are still trapped?, answer: four | question: What is the Death toll doing?, answer: rose to 104 | question: What is the number of miners hospitalized?, answer: Sixty | question: How many miners  were hospitalized?, answer: Sixty | question: Who is still trapped?, answer: four workers