Local residents and rescue workers gather at the site of bus accident in Kohistan, Pakistan, on Wednesday. AP

Gulf Today Report

A passenger bus carrying construction workers of Dasu power plant project plunged into a ravine due to a mechanical failure resulting in leakage of gas that caused an explosion, killing at least 13 persons including nine Chinese engineers, officials said on Wednesday.

Several others were injured in the incident near the Dasu hydropower plant in Upper Kohistan, Khyber Pakhtunkhwa (KP) province, according to the officials.

Soldiers move from an army helicopter an injured Chinese national after a bus fell into a ravine in Kohistan. AFP

According to media reports, Beijing said it was a bomb attack but Islamabad called a vehicle failure. The Chinese embassy in Islamabad confirmed that nine of its citizens died in the incident. Terming the explosion a bomb attack but not giving more detail.

Pakistan's Foreign Office (FO) said in that the Chinese engineers and accompanying Pakistani workers were proceeding to their workplace in Upper Kohistan, when the gas blast happened and the bus veered off the road.

A Chinese national, who was injured in the bus accident, is helped by locals at a hospital in Kohistan. AP

The bus plunged into a ravine after a mechanical failure resulting in leakage of gas that caused an explosion. ... Further investigations are underway, the FO said in a statement said.

Foreign Office said it was in close contact with the Chinese embassy in Islamabad, adding in a statement: Pakistan attaches great importance to the safety and security of Chinese nationals, projects and institutions.

Soon after the incident, Deputy Commissioner Arif Khan, Upper Kohistan, said in a statement that the accident place early in the morning when a bus was carrying more than 30 construction workers, including Chinese engineers, from the Barseen camp to the Dasu plant site.

A Chinese national, who was injured in the bus accident, receives initial treatment at a hospital in Kohistan. AP

He said other than engineers, FC personnel and local labourers were also aboard the bus when an explosion — the cause of which has yet to be ascertained — took place.

The Water and Power Development Authority, which constructing the dam, in a statement, also termed the incident an accident.