The majority of notices - notices of concern, improvement, prohibition and non-disturbance notices - by the regulator were also issued to surface coal mines, according to the Mine safety performance report 2019-2020.

This compares with all previous years of the 10-year reporting period, in which the majority of notices were issued to underground coal mines.

However, of the 70 serious injuries notified, the majority still occurred in underground coal mines.

There were 197 lost time injuries reported, with 60% occurring in underground operations.

Since 2010-11, the lost time injury frequency rate has steadily declined over the reporting decade, marking an overall 50% decrease.

"The incident notification frequency rate increased 7% compared to 2018-19," the regulator said.

"A 34% reduction in hours worked in underground coal mines from 2012-13 has contributed to the overall changes in INFR.

"Dangerous incidents and potentially dangerous incidents are the predominant incidents notified in surface coal mines while in underground coal mines, other high potential incidents represent the greatest proportion of incident notifications across the most recent four-year period."

There were 563 notices issued in the coal sector, a 14% decrease from 2018-19, with improvement notices accounting for nearly half.