The company did not specify the duration of the closure, which follows a precautionary decision announced on Thursday involving the closure of the open pits and stoppage of processing.

St Barbara said security risks had escalated rapidly to an unacceptable level over the weekend, with 100mm of rain having fallen in the four days to April 4.

The extreme rainfall last week developed into Tropical Cyclone Ita and was reported to have accounted for 500mm of rain in one 24-hour period.

“The ensuing flooding caused significant damage to main roads, including the only access road to the mine and one key bridge,” St Barbara said in a statement today.

“This damage has isolated the minesite from critical supplies of fuel necessary for onsite power generation, as well as food and medical supplies.”

Conditions onsite are considered potentially dangerous to the operation’s 200 personnel, the majority of who are Solomon Islanders.

The company said the evacuation was consistent with its highest priority of securing the workforce’s safety.

It said it was in continuing discussions with the Solomon Islands government regarding the future of the mine and would provide an update in a quarterly report due to be released later this month.

For the six months to December, Gold Ridge produced 29,431 ounces of gold, representing 15% of the company’s total gold production for the period.

Shares in St Barbara were last trading 8.9% lower at A25.5c.