An overloaded school minibus crashed head-on with a truck in rural western China on Wednesday, killing at least 18 kindergarten children on their way to class, officials said.

Two adults -- the driver of the minibus and a teacher at the kindergarten -- also died in the accident, said an emergency official surnamed Fan. News of the crash ignited public anger across China, highlighting an under-funded education system that especially shortchanges students in remote areas.

The bus had nine seats, but Fan said it was jammed with 62 children and two adults when it collided with the truck in China's Gansu province, leaving the orange school vehicle crumpled and twisted. Authorities blamed the overloading for the accident, the official Xinhua News Agency said.

Four children and the bus driver died at the scene, said Fan, the director of the emergency office of the Gansu provincial work safety bureau. Gao Shaobo, head of traffic police in Zhengning county, where the school is located, later said that 20 people had died and 44 were still hospitalized -- two in critical condition and 12 with serious injuries.

The impact of the crash drove the front of the minibus back into the seats, ripped open the top and buckled the sides of the vehicle, while the front of the truck was damaged only slightly. Xinhua reported that the truck was loaded with coal, but Gao told state broadcaster CCTV that it was used to transport stones but was empty at the time of the accident.

The bus was on its way to the Little Doctor Kindergarten on the outskirts of Qingyang city after picking up the children -- aged 5 and 6 -- when the accident happened, Gao said. "The van was driving on the wrong side of the street. Both the truck and the van were going at high speeds at the time," he said. The two people in the truck were not injured, and the driver has been detained, he said.

The bus was run by the kindergarten, Xinhua said, citing Li Yuanqing, a government press official with Zhengning county.

Such overcrowding on school buses is common in China, and accidents happen frequently because of poorly maintained vehicles and poor driving habits. State television aired a story in September about a minivan with eight seats that was stopped while carrying 64 preschoolers.

Wednesday's school bus accident appeared to be one of the worst in China in recent years. In December, 14 children died when their school bus plunged into a creek in heavy fog near the central city of Hengyang. Crashes have become a feature of Chinese life as safety habits have failed to catch up to the rapid growth in road traffic amid the buoyant economy.

Chinese Twitter-like microblogs exploded with public anger after Wednesday's accident, registering hundreds of thousands of posts within hours of the news.

Many made comparisons to the quality of U.S. school buses, some by attaching a photo purporting to show a Hummer smashed under the rear fender of a school bus in Indianapolis. "Look at American school buses ... Our school buses are irresponsible when it comes to children's lives," ran the heading attached to many posts.

Beijing has made a concerted effort to rebuild and improve a public education system that had withered with the collapse of centrally planned socialism in the 1990s. Central government spending on education has steadily grown in recent years, rising a projected 16 percent this year to 296 billion yuan ($46 billion), about three-quarters of it given to local governments.

The overall figures mask great disparities, with rural areas and small cities like Qingyang chronically short of funds. Some local governments lack funds to pay teachers, who in egregious cases have charged parents extra fees to teach their children the required curriculum.

Little Doctor Kindergarten, however, falls outside the formal school system. Privately run, the school serves mostly children from farming families, according to the education bureau of Zhengning county.

Qingyang and its surrounding rural areas have seen fast, chaotic growth in recent years. The area sits amid arid hills along the middle reaches of the Yellow River, where Chinese civilization first flourished but which is now known for its poverty. Rural incomes in the region average about 3,660 yuan ($570) per person, about one-fourth the level of city dwellers. More than 120,000 rural residents in the area lack access to clean drinking water.