MANSEHRA: Thirteen people, including nine Chinese nationals, two personnel of the Frontier Constabulary (FC) and two locals, were killed and 28 others sustained injuries when a coach carrying them to an under-construction tunnel site of the 4,300-megawatt Dasu hydropower project fell into a ravine in the Upper Kohistan area after an explosion on Wednesday.

According to eyewitnesses, three vehicles were on their way to the Dasu dam site in a convoy after picking up Chinese labourers in the morning from Barseen camp — some eight kilometres from Dasu district headquarters of Upper Kohistan — via the Karakoram Highway when the blast occurred.

Sources privy to the investigation said a Chinese national was missing and search for his whereabouts was under way.

“After the explosion the coach fell into the riverside but the two other vehicles, a coaster and a jeep, remained safe in the incident,” one of the eyewitnesses said.

Soon after the incident, army helicopters airlifted the bodies and the injured, including 33 Chinese nationals, to the Combined Military Hospitals in Abbottabad and Gilgit.

In the meantime, the FC personnel cordoned off the area until police and other investigating agencies arrived at the spot and started geo-fencing the area.

Wapda Chairman retired Lt Gen Muzammil Hussain rushed to Dasu and monitored the rescue and relief operation at the site.

There were conflicting reports about the cause of the tragic incident.

Pakistan’s Foreign Office (FO) said “leakage of gas” caused by a “mechanical failure” resulted in the blast in the bus after which it plunged into the ravine.

Chinese Foreign Ministry spokesman Zhao Lijian said in a tweet: “China is shocked & saddened at reports of casualties in the incident in Pakistan’s Khyber Pakhtunkhwa Province. We mourn for those who lost their lives & express sympathy to their families & the injured.”

The official statement issued by the Chinese embassy said the bus was “hit by blast on its way to the construction site”.

The statement did not elaborate the cause of the blast, but it advised the Chinese living in Pakistan to “stay on alert, pay close attention to the local security situation, strengthen security protection, take strict precautions, and stop going out unless necessary”.

The Chinese embassy, however, noted that investigations were under way. Both Chinese foreign ministry and the embassy in Islamabad praised Pakistani security forces handling of the situation after the blast.