China's president has made an emotional appeal to search and rescue crews in the country's earthquake-affected areas. He told them not to give up hope of finding more survivors.

"Although the time for the best chance of rescue, the first 72 hours after an earthquake, has passed, saving lives remains the top priority of our work," said Hu Jintao during a visit to the disaster zone.

"Quake relief work has entered the most crucial phase," Hu said. "We must make every effort, race against time and overcome all difficulties to achieve the final victory of the relief efforts."

Crews were given a boost Friday after finding 33 survivors. They had spent about 100 hours buried beneath the rubble of crumbled buildings.

Aid and rescue efforts were hampered, however, as an aftershock reminded residents and emergency crews just how tumultuous the region remains.

The tremor -- measuring magnitude 5.5 -- created havoc in parts of the devastated province of Sichuan. China's official Xinhua News Agency said Friday's aftershock sparked landslides, destroyed roads, and buried a number of vehicles. However, no casualties were reported.

The aftershock struck as residents tried to come to grips of the aftermath of Monday's quake, which many say is the worst disaster to hit China in three decades.

The official death toll following the 7.9-magnitude quake has reached 22,069 but the government has said the figure will likely reach 50,000.

But even as soldiers continue to aid survivors and look for others who may still be buried beneath toppled buildings, Chinese government officials are trying to control swelling anger. Many wonder why buildings -- particularly schools -- were not quake safe. The questions do appear to concern the government, which has taken the unusual step of responding to queries via the Internet.

"If quality problems do exist in the school buildings, we will punish those responsible severely and give the public a satisfactory answer," Han Jin, a Ministry of Education official said on a state-run forum.

Meanwhile, the government has dispatched 130,000 soldiers and police to help in the aid and rescue effort.

"For several days now there were some communities that were still cut off from rescue efforts but today a lot of the soldiers got into those areas so we'll likely see a more realistic number of how many have been killed in this earthquake in the coming days," CTV's Steve Chao reported Friday from Chengdu.

In total, The Associated Press reported that about 10 people were rescued alive Friday.

A nurse, trapped for 96 hours in the debris of a clinic in Beichuan county, was among those found on Friday.

Volunteers heard a call from the ruins of an apartment building and spent more than four hours rescuing the middle-aged woman.

"She had the will to live,'' said Xu Tao, one of the volunteers. "I'm just exhausted."

Another man was rescued Friday from the wreckage of a fertilizer plant near Shifang city.

The Chinese government said it has allocated a total of $772 million for earthquake relief.

China has also received $457 million in donated money and goods to help with the rescue efforts.

With files from The Associated Press