The 30 major ports in China have total iron ore stocks of 97.92 million tons, according to figures from mysteel.com, a steel industry information provider.
High stocks and declining prices have increased the risks for iron ore traders, who are facing increasing financial pressure to repay loans. Meanwhile, steel factories are more cautious when purchasing raw materials.
However, China still imported 58.31 million tons of iron ore in June, a slight decline compared with the 63.84 million tons imported in May.
"China has always played the role of savior of foreign iron ore miners," said Zhang Lin, senior analyst at the Lange Steel Information Research Center. "The steel market is weak, which leads to falling iron ore prices. However, the price is not below $100 yet."
China's stable imports of large quantities of iron ore may be the source of the foreign giant miners' confidence, Zhang said.
Rio Tinto Plc said on Tuesday that the company had a record-high output of 120 million tons of iron ore in the first half of the year, up 4 percent year-on-year. The company estimated that it will produce 250 million tons of iron ore in 2012.
BHP Billiton Ltd, another giant mining company, said on Wednesday that its iron ore output in June increased 15 percent to 40.9 million tons.
It said it will have a total output of 159 million tons this year, also a record figure for the company. BHP Billiton is making efforts to achieve its annual output target of 220 million tons in 2014.
Fortescue Metals Group, the third-largest Australian iron ore producer, said its output increased 54.7 percent to 19.16 million tons in the second quarter. The company plans to sell 55.8 million tons of iron ore in the 2011-2012 fiscal year, a 40 percent year-on-year increase.