Six people who fell into a river following a bridge collapse in central China's Hunan province remain missing despite an expanded downstream search, local authorities said Monday.

The 120-meter bridge, which connects two townships in Pingjiang county, collapsed around 8:50 a.m. Sunday after being hit by three sand dredges flushed downstream by the worst floods experienced in the county in a century.

Nine people subsequently fell into the Changjiang River, with three rescued thus far.

An elderly couple, their two granddaughters and another relative are among the missing, said Li Junrong, a relative of the couple.

Rescuers braved further rains on Monday to expand the search for the six missing. Three excavators have also been deployed to help search under the collapsed bridge.

Six hours of heavy rains early Saturday pushed up water levels on the Changjiang River by three to four meters, according to Li Zuoru, a local official.

The bridge had been shut down by transportation authorities since Saturday morning following rainstorms that toppled 3,500 homes and forced more than 28,880 people to evacuate.

Despite the presence of both a warning sign and a watchman, some villagers still forced their way onto the bridge, Li said.

Witnesses said there were people riding motorcycles on the bridge when it collapsed.