BEIJING — China's coal mines have been boosting intelligent mining technologies to reduce accidents with more robots working underground.

The number of pieces of machinery equipped with smart mining technologies reached 494 at the end of 2020, up 80 percent from the previous year. The growth has been rapid as the number was only three in 2015, according to the National Mine Safety Administration.

Nineteen kinds of robots were working in underground coal mines for mining, drilling and patrolling at the end of 2020.

The country has closed 5,464 coal mines that were vulnerable to accidents over the past five years.

China saw 122 coal mine accidents in 2020, down 28.2 percent year-on-year, and 225 related deaths, down 28.8 percent.

There were 312 accidents in non-coal mines in 2020, down 14.9 percent year-on-year, and 348 related deaths, down 16.9 percent.

In the next five years, the coal mine sector will continue to increase smart mining and phase out outdated production facilities, said Huang Yuzhi, head of the administration.