Amid the roaring noise of motors, several boats carrying rescuers cut through murky floodwaters and charged toward the roofs of buildings that rose out of the water in the distance.

The rescuers were searching for trapped villagers in Lianhu town of Poyang county in Shangrao, Jiangxi province, which was isolated due to the flooding of Poyang Lake, China's largest freshwater lake, after heavy downpours.

A team of 25 people from Condor Rescue, a professional rescue team from Luoyang, Henan province, volunteered to help.

They set off from Luoyang on Wednesday with six boats, looking for people in need of help. They went to Poyang twice, and by Sunday they had saved more than 70 people who had been trapped there.

"It's where the floods are heaviest that we play our role," said Chen Yantao, a member from the team.

On Saturday, Poyang county raised its emergency response for flood control to Level I, the most severe, as many villages in the county were inundated by water from Poyang Lake.

The evacuation of residents began on Wednesday in Lianhu, a town with 31 villages and a population of more than 60,000, but some remained there, mostly older people who did not want to leave their hometown.

On Sunday, the town asked for emergency rescue assistance. Boats were needed to evacuate people as villages were largely submerged and roads into the town were cut off.

Meanwhile, the water level was still rising.

"The water level goes up about a meter each hour. We can't afford to lose even half an hour," Chen said. Guided by villagers, the rescuers sailed around looking for people.

"The highest water level reached 23 meters, and the tops of trees and utility poles were sticking out of the water," he said.

Giant lotus seedpods, a specialty of the town, were washed up by the floods, floating with weeds, crops, sticks and water snakes on the surface.

The closer the boats got to the submerged villages, the more vegetation there was. Rescuers sailed alongside rows of treetops above the water surface.

They looked around warily while shouting for anyone who needed help.

"We have to prevent the motor from getting tangled, and prevent nails and branches from cutting the rubber boats," he said.

Chen said that some villagers, especially those in their 50s and 60s, were very reluctant to leave because they worried about their families' properties.

"When the water rose up to the first floor, they moved to the second floor. When it went to the second floor, they moved to the third floor, and finally the roof," he said, adding that villagers thought the flood this year was the same as usual and they just needed to wait for it to recede. Chen spent some time persuading them to leave.

In the afternoon, the team found four people who were trapped on an island, which is really a hill that had been mostly submerged by the flood.

Chen said the four had stayed on the hillside for three days, but they had only brought food for one day with them because they thought the flood would be over soon.

"They were starving and started eating immediately when they boarded the rescue boats," he said.

Another four people on the hill were unable to call for help because they couldn't get a cellphone signal.

One of them, a man in his 30s, jumped into the water and swam to look for help.

"He was good at swimming, so when he saw the situation was urgent, he risked jumping into the water to swim for help," said Wu Zhiqiang, another rescuer.

The man eventually came across rescuers and directed them to the hill to help the others who were stranded.

The search continued until 4:30 pm on Sunday, with 33 villagers safely evacuated during the day.

On Sunday night, the team made plans for rescue in other places.