A crane has toppled at Gina Rinehart's Roy Hill mine site in Western Australia's Pilbara as it was being evaluated by an inspector.

Nobody was injured in the incident, which occured yesterday when the plant inspector was assessing equipment on the $10 billion iron ore mine's construction site.

The inspector was there due to a prohibition notice issued by the Department of Mines and Petroleum, which had told Roy Hill to urgently improve safety standards following earlier incidents involving cranes and elevated working platforms.

The company said it has suspended cranes operated by contractors Samsung C&T and its subcontractors, including Leighton Construction, NRW and Kerman at the site in the wake of the incident, pending an investigation.

"Roy Hill recognises there have been serious issues in regards to safe lifting and crane operations being undertaken by head contractor, Samsung C&T and Leighton Construction at the mine processing plant construction site," Roy Hill chief executive Barry Fitzgerald said in a statement.

"The incidents that have occurred are not acceptable; and we continue to cooperate fully with the DMP to ensure lifting operations can be undertaken safely and without incident.

"We have suspended all crane activities including verification and assessment pending an investigation into this incident to understand the root cause."

He said Roy Hill took the issue very seriously, and it did not reflect values on the site.

He said the company had escalated the issue to the "highest levels" with Samsung C&T and Leighton Construction and had sent one of their own senior safety employees to the contractor, to "drive change in regards to safe lifting operations".