At least 58 people, including 21 women and 19 children, were killed when a passenger bus Tuesday collided with a truck in Pakistan's Sindh province, police said.Over 20 injured people were in critical condition in hospital, The News International reported citing police officials.The accident took place near Theri Bypass in Sukkur district, Xinhua reported.The accident happened when the bus driver ostensibly fell asleep while driving and hit a truck coming from the opposite direction.There were over 80 people in the bus which was on its way to Karachi from Swat district. The fate of the remaining passengers was not yet known.President Mamnoon Hussain expressed grief over the accident and directed the hospital administration to provide best possible medical treatment to the injured.Sindh province Governor Ishrat Ibad also expressed his condolences to the family members of the victims.