At a televised press conference, Ai Yang, a Chongqing government spokesman, said 74 people were missing, including 47 workers at an iron ore mine, 21 local residents, two telecom company workers and four passers-by.
Ai said that so far no bodies have been found when asked about the report of 26 deaths, but he did not deny the report.
More than 500 rescuers were searching for survivors, the official Xinhua News Agency said.
Chinese President Hu Jintao and Premier Wen Jiabao ordered local authorities to "spare no efforts" to save those buried, Xinhua said.
Rescuers were also digging a channel to relieve a barrier lake that formed when the landslide blocked a river, CCTV said.
Densely populated Chongqing is rich in iron ore, natural gas and other mineral resources, and industrial accidents are common.
An official with the Chongqing work safety supervision bureau, who would give only his surname Dong because he was not authorized to speak to media, said the landslide did not appear to be related to mining activities.
Similar landslides have been reported around China, including one last year where at least 277 people were killed when a shoddy holding reservoir burst and a three-story wave of mud and iron-mining waste inundated a valley in Shanxi province in northern China.