More than 3,900 people remain missing - of whom more than six hundred are workers believed to be trapped in a vast network of mud-filled tunnels at hydropower sites along Trishuli River. Engineers have been pumping air into the tunnels - and while a team did manage to gain entry to one of them, it withdrew after finding no-one there. "I wish we could find him. I wish he would come home”, Anushila Bhandari, wife of Aurus Bhandari, a 33-year-old engineer missing on a project site, told BBC Nepali. Nepalese Prime Minister Balendra Shah said on Monday that 279 people had been rescued from the sites. The rescue operation is being spearheaded by an international team made up of Chinese and Nepalese military personnel, while experts from India, Korea and Australia are also involved. "I still have a 50% hope that he is alive because there is an oxygen system inside”, Sita Pandey, whose husband was working in the plant when the floods hit, told Nepalese daily Kantipur. Nepal relies heavily on hydropower and has spent years developing the projects along its mountainous river systems. At least 11 projects either completed or under construction were damaged in the floods, authorities said. Rescuers began pumping air into a tunnel over the weekend, but the families of those trapped say that should have been done earlier. A team was able to get into a tunnel leading to one hydropower plant earlier on Monday, but retreated after no one was found there. "The longer it takes, the more our hope dies. This operation must move much faster because every second is meaningful to us”, Jiban Khadka, whose relative is also trapped inside the plant, told Kantipur. "It's a frustratingly slow operation”, Khadka added. (BBC)