Over 20 workers are believed to have trapped in an under construction expressway tunnel which collapsed in China's Fujian province Friday.The workers were trapped after "a 30-meter long section of the expressway tunnel in Longyan City collapsed", a rescue official told Xinhua.Debris estimated at 5,000 cubic metres have blocked the tunnel, which had been under expansion construction to accommodate the expressway linking Xiamen City of Fujian and Chengdu, the provincial capital.While the rescue operation was still underway in the morning, there was no immediate information about any casualty.