The Australian government has decided to extend its review of two other Chinese firms' investments in the country's miners just one week after a similar extension was granted to examine Aluminum Corp of China's (Chinalco's) investment in Rio Tinto.

The country's Foreign Investment Review Board announced that it would extend its probe of the takeover of OZ Minerals by China's Minmetals by as long as 90 days from March 24, OZ Minerals said on Monday.

The Minmetals Corp, China's largest metal trader, last month proposed to buy the Australian mining firm for A$2.6 billion ($1.7 billion) in cash to ensure adequate supplies of non-ferrous metals. The Melbourne-based company operates zinc, lead, copper, gold and silver mines in Australia and overseas.