BEIJING / GUIYANG - Floods killed 21 people and left at least 31 others missing in Guizhou province as authorities upgraded the emergency response to Level 3 from Level 4 on Tuesday.

The Ministry of Civil Affairs said it raised the emergency level and dispatched vice-minister Jiang Li to lead a working team on behalf of the State Council, or Cabinet, to gauge the extent of the disaster and oversee relief efforts.

Some 45,000 residents in Wangmo county, one of the worst-hit areas, have been evacuated since floods swamped the area on Monday, Tang Quanshu, from the county's flood prevention office, said.

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Flooding had caused the collapse of 300 houses and left 2,400 submerged, while 5,500 hectares of farmland were under water, Tang added.

Economic losses amounted to 1.34 billion yuan ($206 million), according to Xinhua.

Hundreds of tents had been distributed and hundreds more were on the way.

About 1,000 soldiers, armed police officers and militiamen had been dispatched to the county to help with relief efforts, Li Zechun, an official at the local publicity department, told China Daily.

He added that more than 900 families had been sheltered in tents.

Floods had so far hit 11 cities and counties across Guizhou, affecting more than 270,000 people, the provincial civil affairs bureau said.

Despite the flooding, students from Wangmo sat the national college entrance examination on Tuesday. Among the 902 students registered for the examination, 900 took part, Li said.

"We will do our best to ensure that all students are able to take the exam," Tu Zhangyou, deputy head of the county, said.

Yang Bofu, a local student, said he and other students were moved to a hotel after his rented apartment was flooded.

The local government provided free meals to students, he said.

In Hunan province, floods, caused by heavy rain since the start of June, affected about 1.38 million people in five cities and autonomous prefectures.

The economic cost was estimated at 587 million yuan, a report released on Tuesday by the provincial drought relief and flood control office said.

The National Meteorological Center forecast that rain would continue in the drought-afflicted middle and lower reaches of the Yangtze River for the next week, which may lead to severe flooding.

Torrential downpours are also expected to hit the eastern provinces of Zhejiang and Jiangxi.

Xinhua and Feng Zhiwei contributed to this story.