The death toll has risen to nearly 40 after a school bus carrying more than 100 young people overturned in Pakistan’s Punjab province on Monday evening, police said on Tuesday.

The accident happened near the town of Kallar Kahar, located in Chakwal District, where the students had visited a salt mine and joined a school picnic. They were on their way back to Millat Grammar School in the city of Faisalabad when it happened.

More than 100 young people were on board the bus when it overturned and plunged into a ditch due to a suspected brake failure. Photos from the scene showed the heavily damaged vehicle with the seating area completely crushed.

As of Tuesday morning, police said at least 30 students, six teachers and a school principal were killed as a result of the accident. A spokesman said all the students who were killed were believed to be between the ages of 12 and 20.

In addition to those killed, officials reported that around 70 people were injured and taken to area hospitals where an emergency was declared. Some of those injured were in an extremely critical condition, and officials fear the death toll will rise further.

Hours after the accident, President Asif Ali Zardari expressed his ‘profound grief’ over the loss of life. “The President prayed Allah Almighty to rest the departed souls in eternal peace and grant courage to the bereaved families to bear the loss with fortitude,” a statement issued by state-run media said. It added that the president directed officials to provide the best medical treatment to those injured.

Road accidents are common in Pakistan with more than 5,500 fatalities in 2007, according to the most recent figures released by national police. Many accidents are the result of poor infrastructure and the disregard of traffic laws.

Last Friday, seven people were killed and twelve others were injured when a passenger bus fell down a trench in northwestern Pakistan. The accident occurred in the Ashiri Drah area in the Upper Dir district of Khyber Pakhtunkhwa province.