A passenger bus skidded off a mountain road and plunged into a deep gorge in northern India on Monday, killing 16 people, including schoolchildren, a government official said. Rescue workers pulled the seriously injured from the wreckage of the vehicle and sent them to a hospital, Ashutosh Garg, senior district commander of Kullu district in Himachal Pradesh state, told the Press Trust of India news agency. Another official, Prashant Sirkek Singh, said around 20 passengers were traveling in the bus. Photos shared on social media showed responders trying to rescue survivors from the mangled yellow bus cube. The exact cause of the crash was not immediately known. Indian Prime Minister Narendra Modi expressed his regret over the accident. Fatal road accidents are common in India due to reckless driving, poorly maintained roads and old vehicles. More than 110,000 people are killed every year in road accidents across India, according to police.