At least 20 people were injured after a 40-year-old building partially collapsed early on Wednesday in Leshan City, in southwest China's Sichuan Province.

Rescuers freed more than 30 survivors from the debris who are being treated at two local hospitals. No deaths have been reported, said a spokesman for the city's public security bureau.

Leshan City government spokesperson Lei Dingbo estimated 20 people were injured, including a fireman who was helping with the rescue work. Most people suffered cuts or bone fractures.

"Two of the cases are serious but none is critical," he said at a press conference on Wednesday morning.

The rear of the former agricultural exhibition center in downtown Leshan collapsed at around 7:20 AM when at least 90 people, mostly retirees, were inside attending a free medical lecture, witnesses said.

One third of the roof fell in, and bricks and wood covered an area of more than 200 square meters.

Fortunately, most of the people were sitting in the front and were able to escape the site without being injured.

Ma Guoquan, one of the injured, is now being treated at the city's first aid center. The 73-year-old man suffered a fracture of the pelvis.

"We gathered at the exhibition center for a medical lecture, but actually it was a promotion for a medicine for tympanitis," said Ma.

"We were listening to the lecturer, when the wooden beams suddenly fell with a huge bang," recalled Ma. "A big piece of wood hit me at waist and it hurt so much I could barely stand."

Shi Keming, 87, who is said to be the oldest victim of the collapse, is still in danger with head and waist injuries.

"My father often does morning exercises at the square near the center, but who could imagine that this would happen to him," said Shi's daughter.

The exact number of casualties is being investigated, said Luo Jiaming, head of the city's publicity department, blaming the accident on the heavy rain that hit Leshan over the last two days.

Investigation shows that the lecture was organized by a farmer from nearby Meishan City who did not file an application to hold the lecture, said Luo.

"The police haven't ruled out the possibility that this may be a fraud case targeting senior citizens," said Luo.

According to Luo, the square nearby is a popular place for many local residents to do exercises.

"Police said they (the organizers) maybe chose to hold the lecture early in the morning because it is the time most retirees do their exercises in the square," said Luo.

The two-story exhibition center was built in 1959. It is largely unused except by senior citizens who like to dance in its large halls.

"So far as I know, the building has never undergone a safety inspection," said Huang Weiming, deputy director of the city planning bureau.

Leshan is a major tourist destination about 100 kilometers southwest of Sichuan's provincial capital Chengdu. The city is famous for the Leshan Grand Buddha, which is 70 meters tall and was carved from a cliff face.

(Xinhua News Agency June 7, 2007)