At least 12 persons, including nine Chinese engineers and two Frontier Corps personnel, died and several others were injured on Wednesday in a bus "attack" near the Dasu hydropower plant in the Upper Kohistan district of Khyber Pakhtunkhwa.

Initial reports from officials on what caused the deaths appeared conflicting; however, Adviser to the Prime Minister on Parliamentary Affairs Babar Awan, speaking on the floor of the National Assembly, termed it a "cowardly attack" and said that it would "not divert attention from the special initiatives between Pakistan and its neighbours".

Condemning the attack, Awan said that he will ask Interior Minister Sheikh Rashid Ahmed to give a briefing on the country's security situation and take this house into confidence regarding the incident.

Hours later, the Foreign Office contradicted reports of an attack, saying that the bus "plunged into a ravine after a mechanical failure resulting in leakage of gas that caused a blast". The FO also put the death toll at 12, including 9 Chinese nationals, up from earlier reports of 10 deaths.

The Chinese foreign ministry spokesman, however, condemned the incident as a “bombing”.

Special Assistant to the KP Chief Minister on Information Kamran Khan Bangash had earlier said a high level delegation has left for Upper Kohistan, adding that officials will shortly inform the people and the media of the ground realities. "The media is advised to avoid speculating on the matter," he said.

Bangash said a large number of security officials were deployed to protect Chinese nationals. Those who are in critical condition are being shifted via helicopter, he said. A large number of Rescue 1122 ambulances and officials have reached the spot, he added.

Beijing asks Pakistan to investigate incident

Meanwhile, China asked Pakistan to thoroughly investigate the incident.

Condemning the attack, China's foreign ministry spokesman Zhao Lijian expressed his “shock and condemnation over the bombing”.

Lijian urged Pakistan to “severely punish the perpetrators“ and “earnestly protect the safety of Chinese nationals, organisations and projects” in the country.

In a statement, the Chinese Embassy in Pakistan "strongly condemned the incident", expressed condolences with the victims and the injured, adding that it "will do its best with Pakistan to deal with the incident".

"The Chinese Embassy in Pakistan hereby reminds Chinese citizens, enterprises and projects in Pakistan to attach great importance to them, pay close attention to the local security situation, strengthen the safety of project personnel, take strict precautions, and do not go out unless necessary," the statement read.

It, however, added that Pakistani authorities "were investigating the cause".

Later in the day, Foreign Minister Shah Mahmood Qureshi offered his condolences to his Chinese counterpart Wang Yi on the "tragic incident in which a bus carrying Chinese workers plunged into a ravine after developing a mechanical failure".

Qureshi asked Yi to convey the condolences to the families of those who lost their lives in the incident, according to a statement by the FO.

Conflicting reports

Soon after the incident, Upper Kohistan Deputy Commissioner Arif Khan Yousafzai had told Dawn.com that it took place around 7:30am when a coaster was carrying over 30 workers, including Chinese engineers, from the Barseen camp to the plant site.

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

The Foreign Office, in a statement later in the afternoon, said the bus had "plunged into a ravine after a mechanical failure resulting in leakage of gas that caused a blast".

"Pakistan and China are close friends and iron-brothers. Pakistan attaches great importance to safety and security of Chinese nationals, projects and institutions in Pakistan," the FO statement said.

Meanwhile, the Water and Power Development Authority (Wapda), in a statement, also termed the incident an "accident".

A Wapda spokesman confirmed that employees of a Chinese company were travelling in the bus, adding that rescue efforts were under way at the site of the incident and the injured were being shifted to a hospital.

He added the site had been cordoned off by police and Rangers.

The injured were being shifted to Dasu Rural Health Centre, officials said.

A senior police officer told Dawn.com that it was unclear what had caused the incident, adding that mobile networks are not functional in the area which was making it difficult to get information.

"At the moment we are not clear what exactly happened, whether it is blast or an accident," the official said, adding that once police complete initial investigation, the situation will become clear.

He said KP police chief Moazzam Ansari has left for Upper Kohistan on a helicopter.

This is a developing story that is being updated as the situation evolves. Initial reports in the media can sometimes be inaccurate. We will strive to ensure timeliness and accuracy by relying on credible sources, such as concerned, qualified authorities and our staff reporters.