The family of a woman who was knocked down by a Hong Kong truck driver in Shenzhen has accused him of kidnapping her four-month-old son, who she was pushing across the road in a stroller. Li Yun, 20, originally from Guizhou , was crossing Busha Road in Shenzhen's Longgang district at about 7am on Sunday when she was hit by a Hong Kong-licensed truck driven by Leung Koon-bui. Leung, a Hong Kong resident, allegedly fled the scene, leaving Li seriously injured on the road. A witness said the truck ran over the stroller and dragged it away with the baby still inside. The baby was still missing yesterday. Shenzhen police said Leung returned to Hong Kong less than an hour after the accident. He later returned to Shenzhen and police are detaining him. Li, who was being treated for a fractured skull at Nanling Hospital yesterday, said: 'The truck suddenly appeared and then I was knocked down and lost consciousness.' Her mother-in-law, Wang Guizhen, said witnesses told her the truck did not stop. 'Many witnesses waved at the driver to get him to stop, but the driver ignored them and sped away,' she said. 'They even heard our baby cry in the stroller. It's definitely a case of the driver kidnapping our baby since the baby was alive at that moment. And so far no body has been found by police.' Police officers contacted Leung's company in Shenzhen at about 10am on Sunday, demanding that he return to Shenzhen to assist in the investigation. A Hong Kong police officer said Shenzhen police had sought help from the force's liaison bureau to find the truck and its driver. 'The man had surrendered to Shenzhen police before our officers were sent out to find him,' the officer said. Leung said he was not aware there had been an accident and said he found an empty stroller under his truck when he passed the Tanglangshan Tunnel on the Nanping Expressway. He said he pulled the stroller from beneath his truck and discarded it beside the expressway, according to Shenzhen police. They mobilised more than 100 officers to search for the baby and found the stroller, with blood on it, at 10pm on Sunday. Leung has been detained on hit-and-run charges. Leung's company was paying for Li's medical treatment, police said. Li's mother-in-law holds out hope the baby is alive. 'We believe the baby is still alive and may have been hidden somewhere in Hong Kong by the driver,' Wang said. Lying in the hospital bed, the weeping Li said she was very worried about her child. 'I am very worried about his safety,' she said. 'I am desperate to see my little boy.' Shenzhen police are seeking information from the public.