BHP Billiton Ltd. (BHP) said Thursday it has closed the Perseverance nickel mine in Western Australia state after a rockfall trapped a miner underground.

BHP said the rockfall was caused by a seismic event and that all employees and contractors were safe and accounted for, but one employee remained trapped underground.

The worker took refuge in a safety chamber underground and, at 1030 GMT, BHP said he had passed the rockfall and was expected to be out safely within half an hour.

"As a result of the incident, operations at the Perseverance underground mine have been suspended," BHP said in a statement.

-By Alex Wilson, Dow Jones Newswires; 61-3-9292-2094; alex.wilson@dowjones.com