Tens of thousands of people fled their homes Wednesday along a rain-swollen northeastern river that officials feared would overflow its banks and cause the biggest flood in China since 1949.

More than 20,000 people already had been evacuated from areas around the Nenjiang River, which runs south from the Sino-Soviet border through Inner Mongolia and Heilongjiang Province, said Chen Dekun, Central Flood Control spokesman.Another 40,000 were scheduled to be moved before the river's record-breaking waters reached the industrial city of Qiqihar.