The quake, which the agency said was an aftershock following the 8.0-magnitude May 12 quake, occurred early on Wednesday with its epicenter in Qingchuan County in the city of Guangyuan.
Seven miners were working at the mine when the roof collapsed. Five managed to escape, Xinhua cited local officials as saying.
Thirteen houses collapsed in Qingchuan, but no casualties were reported.
Another three residents suffered slight injuries in the city's Lizhou district when they fled their homes, a local emergencies official said.
The May 12 earthquake in Sichuan, the most powerful to hit the region in thirty years, killed at least 70,000 people and displaced 10 million. Another 18,000 people are missing. Direct economic losses from the quake have exceeded $150 billion.
China has been hit by more than 31,000 aftershocks since May.
