ZHENGZHOU - The partially collapsed viaduct in Henan province was up to the standards and had passed latest quality test, an official with the provincial transportation authorities said on Saturday.

A part of the expressway viaduct collapsed on Friday morning when an explosion caused by a truck loaded with fireworks took place. Ten people died and 11 others were injured in the accident.

Li Qiang, chief engineer of Henan Provincial Transportation Department, told Xinhua reporters that the bridge had passed biennially and monthly inspections and was up to the standards of the national expressway viaduct.

The expressway viaduct, with bidirectional four lanes, opened to traffic in 2001 after three years of construction. The last test in 2011 revealed no safety risks.

In face of the public concerns, Wang Baixing, the country's renowned bomb-disposal expert, said the the power of the blast on the truck that carried fireworks and firecrackers was equivalent to one ton of explosive.

"The crucial reason was that the explosion occurred on special part of the viaduct, blowing off the upper structure of the bridge and pulling down one of its piers," Wang explained.

The collapse occurred around 9 am Friday on a 30-meter-high viaduct in Mianchi County, Sanmenxia City, about 193 km west of the provincial capital of Zhengzhou.

Rescue work has concluded with 11 injured people in stable condition. The probe into the accident is underway, government sources said.