Engineers have arrived at a remote Northern Territory manganese mine to develop a plan to safely recover the body of a worker who is believed to have been killed in a a massive wall collapse last weekend.

Craig Butler, a 59-year-old Darwin married father of two adult daughters, was caught at the bottom of the Bootu Creek open-pit mine in what the industry calls a “wall slip”.

It is not known how long it will take to get to the mining superintendent because the site is too unstable and dangerous to enter.

An estimated 48,000 or more cubic metres of rock and soil fell in the collapse on Saturday afternoon, which occurred during a safety assessment.

The Department of Primary Industry and Resources released a photo showing the massive amount of rubble that fell in the mine, about 110km north of Tennant Creek.

Geotechnical engineers are assessing the stability of the ground.

NT Police, NT Worksafe inspectors and government department officers are conducting an investigation.

“This is an extremely sad situation for all involved and our thoughts are with the family of the mine employee, workers on site and emergency first responders,” the three groups said in a joint statement.

There have been past safety issues at the 14-year-old mine, including at least two previous wall slips.

In 2013, the mine’s owner-operator OM Holdings was fined $150,000 in a landmark ruling in the NT Local Court for causing a collapse that desecrated a sacred Aboriginal site at Bootu Creek known as “Two Women Sitting Down”.

Traditional owner Lizzie Johnson, whose family and clan group were not involved in that legal action which involved the Kunapa people, said the death in an area they regard as their “homelands” was distressing.

She was returning from her nephew’s funeral when an ambulance on its way to the mine drove past, she said.

Multiple groups have claims to the Bootu Creek area but Ms Johnson said her family doesn’t receive any royalties from OM Holdings.

“I am really sorry for that family who are grieving and my family are grieving with them too, especially for young ones missing their father,” she said.

“I feel heavy and I feel really sad about other people controlling and trespassing on our country, they push us aside too without knowing and we don’t see any money from that country.”