'Heartbreaking day': two dead, one injured in underground mine explosion

Emergency services were called to the mine on Endeavour Mine Road at Cobar, about 450km east of Broken Hill, about 3.45am on Tuesday, October 28.

Police said they had received reports that two people had been critically injured in a workplace incident.

When officers arrived, they were told a man, believed to be in his 60s, had been confirmed dead after the explosion.

Two women believed to be in their 20s were brought to the surface, but one had since died, police said.

Police said the second woman was flown to Orange Hospital where she was being treated for hearing damage and shock.

All three are believed to live in Cobar but have yet to be identified, police said.

The Endeavor Silver, Zinc and Lead Mine is located 40km north of Cobar and is operated by Polymetals Resources.

Polymetals executive chairman Dave Sproule said he was "shocked and saddened by the tragic incident".

"The site emergency response team has been activated, and we are working with all relevant authorities," Mr Sproule said in a statement.

He said mining operations have been temporarily suspended.

The company announced a trading halt on October 28, pending a further announcement.

In the request to the ASX, the company said the halt was in relation to "a serious safety incident" at a mine site. It said the pending announcement would include an update on the "consequences of the incident".

The NSW Resources Regulator confirmed it would steer an investigation into the incident, while police will also prepare a report for the coroner.

Cobar mayor Jarrod Marsden said he was struggling to come to terms with the deaths, but the town would need to find strength in community to get through the tough time.

"Two families' loved ones didn't come home from a night shift. Their lives have been changed forever, just decimated by this," he told AAP.

"We're devastated, just in shock and it's impossible to try and find the words to describe it."

NSW Premier Chris Minns and the Minister for Natural Resources Courtney Houssos released a joint statement following the tragedy.

"We extend our deepest condolences to the family, friends and colleagues of the workers who have tragically died in Cobar today," the statement said.

"This is a heartbreaking day for the Cobar community and will be felt across the entire mining industry."

They said the number one priority in any mine must be safety.

"Everyone who goes to work has the right to come home."

"While safety protocols and procedures have greatly improved in mining, these deaths are a sobering reminder of why we need to always remain vigilant to protect workers."

The NSW Mineworkers' Alliance (NSWMWA) said it was "in shock" following the deaths and sent condolences to the workers' friends and family and colleagues.

NSWMWA officials will be on site to offer support to workers and investigate the circumstances.

"We will leave no stone unturned in identifying what has occurred here," spokesman Tony Callinan said.

"This is a tragic reminder that underground mining is a dangerous job," Mr Callinan said. "Events like these send shockwaves through our entire mining industry."

He said it was a "reminder why the union always emphasises safety over production".

NSW Minerals Council CEO Stephen Galilee said the industry was mourning the death of the workers.

"This tragedy highlights the hazards faced by those working in our industry and is a sombre reminder of why the NSW mining industry must never deviate from our commitment to the safety of our workforce as our number one priority."

"The thoughts of tens of thousands of miners across NSW will today be with the families and colleagues of the deceased and injured, and also with the residents of the mining community of Cobar at this extremely difficult time."

Anyone with information about this incident is urged to contact Crime Stoppers: 1800 333 000 or nsw.crimestoppers.com.au.