When 33-year-old Shi Haiqing answered the phone in the safety center at a coal mine in Taiyuan early on Tuesday, he thought the call might be from one of his colleagues reporting on work safety.

But the caller asked: "Can you tell me about the gas density at the position where I am standing now? Can you tell where I am at the moment?"

Shi felt the voice sounded familiar, but lost no time in replying. Taking a glance at the control panel, he said, "The gas density is 0.05 (percent per cubic meter)."

His heart then pounded with excitement after the caller told him, "This is Li Keqiang."

The call took place during the premier's visit to the Guandi Coal Mine in Taiyuan, Shanxi province. After hanging up the phone, Li told the workers that safety is paramount in mining jobs. He also extended New Year's greetings to everyone at the scene.

Li spent two hours inside the mine, which was founded in 1960 and now has about 5,900 workers. He inspected mine production safety and talked with the workers, learning about their living and working conditions.

The two-day visit to Shanxi is Li's first trip of the year. Most of his agenda comprises visits to traditional industries such as coal mines and iron and steel works.

The province has relied for decades on developing its rich mining resources. In 2012, about 56.6 percent of its GDP came from the coal mining industry. But an industry slump both domestically and globally has hit Shanxi hard, especially last year.

During his visit to the Guandi mine, the premier asked several times about workers' salaries.

He arrived at the mine, which lies inside a mountain, at 9 am and boarded a small train used to transport the miners. They work 300 meters underground but their work area is 7 kilometers from where Li boarded the train, and the journey took 40 minutes.

Before getting on the train, Li greeted scores of miners who had just finished the night shift and were about to change out of their dusty uniforms. After a 12-hour shift, the workers, whose faces were nearly half-black with coal dust, stood around the premier.

Li encouraged them to have confidence in the coal market, although current prospects are not looking so good.

"Coal mining still serves as Shanxi's pillar industry. About 60 to 70 percent of the energy that the country requires for its development comes from coal mines," Li said.

The coal mining industry is suffering from "certain difficulties" as the global market does not look too good, he said.

"But we need to have confidence that coal will still be the country's major industry. The difficulties will eventually be conquered," Li added.