The child was found by rescuers searching the rubble of a school in the quake-devastated town of Beichuan, according to state-run Xinhua news agency.

The report said rescuers could hear more voices calling for help in the rubble and were "expecting more miracles."

It did not specify the child's age or gender.

On Thursday, an 11-year-old girl was pulled from the rubble of another school in the badly hit town of Yingxiu.

But officials have played down the chances of finding many more survivors, saying it would be miraculous for anyone to survive under the rubble for more than 72 hours.

Chinese President Hu Jintao, visiting the quake zone on Friday, said relief work had entered "the most crucial phase."

The government estimates that more than 50,000 people have died in Monday's 7.9-magnitude earthquake, China's worst natural disaster in a generation.

Nearly 7,000 schools were destroyed by the earthquake, prompting the government to announce on Friday it had launched an investigation into whether shoddy construction was to blame.