Australia vowed to leave "no stone unturned" on Monday after a plane carrying one of the country's richest men and other mining bosses went missing over dense jungle in western Africa.
Prime Minister Kevin Rudd promised full diplomatic and consular assistance after the twin turboprop plane carrying tycoon Ken Talbot and other top personnel from Sundance Resources disappeared on Sunday.
"This is deeply concerning to all of us," Rudd told reporters.
"All of our diplomatic and consular resources are being dedicated to this... we will leave literally no stone unturned in our efforts to try and help what is a concerning set of developments for these families."
The plane was also carrying two people from France, two Britons and an American, as well as two crew, from Cameroon's capital Yaounde to the Yangadou mine in neighbouring Congo, local authorities said.
The CASA C-212 plane lost contact with ground controllers shortly after take-off on Sunday morning.
Cameroonian authorities suspended their search, involving four search planes and a helicopter, as night fell on Sunday.
Talbot is a non-executive director of Sundance, an iron ore miner, with estimated wealth of USD 840 million US,according to BRW business magazine's latest rich list.