The police in Kunming, Yunnan province, arrested a 25-year-old man suspected of killing 19 people aged 3 to 72, in a remote southwestern village on Thursday afternoon.
The Ministry of Public Security sent a team to investigate the case along with local authorities.
Few details are known since the investigation is in its early stages, but the provincial public security authority said it did not involve terrorism.
Yunnan provincial public security authorities confirmed that 19 villagers from Yema village, Huize county, Qujing city - including four children - were found dead on Thursday morning. The victims were from six families.
The suspected killer, Yang Qingpei, a resident of the village, was arrested at 2 pm on Thursday in Kunming, about 200 kilometers away from the where the crime occurred, the city police said.
Though no official details about motives were released, an anonymous source claiming to be the suspect's student told Chengdu Business Daily that the victims were relatives of Yang, including his uncles.
Yang is married and has worked in Kunming for years, but has been in debt as a result of gambling, the source said, adding that he intended to borrow money from his relatives but was rejected and killed them on Wednesday night.