A day after claiming that a gas leak inside a transport brought about the death of nine Chinese nationals, Pakistan’s information minister Fawad Chaudhry said on Thursday that traces of explosives had been found in the vehicle and psychological warfare couldn’t be precluded in the episode.

Beijing pushed back emphatically in the face of Islamabad’s claim on Wednesday, depicting the occurrence as a “bomb attack” and demanding discipline for the perpetrators and steps to guarantee the safety of the Chinese workforce, foundations, and projects in Pakistan.

Thirteen individuals, including nine Chinese nationals, were killed when a transport taking laborers to the 4,300-MW Dasu hydropower project was hit by a blast in the Upper Kohistan area of Pakistan’s Khyber-Pakhtunkhwa territory.

“Initial investigations into Dassu episode have now affirmed traces of explosives. Psychological warfare cannot be precluded, PM is personally administering all improvements in this regard. Govt is in close coordination with Chinese embassy we are resolved to the battle menace of psychological warfare together,” Chaudhry tweeted on Thursday.

In the face of pressing factors from China on Wednesday to investigate the episode, Pakistan’s Foreign Office had said in a statement that the transport carrying Chinese specialists had “dove into a ravine after a mechanical failure bringing about leakage of gas that caused a blast”.

Specialists referred to images of the transport shared on social media and said the damage appeared to have been caused by a blast, instead of a fall into a ravine. They also scrutinized the dispute that the transport was fueled by gas.

A statement on the occurrence gave by the Chinese embassy in Islamabad alluded to an “attack on the Dasu Hydropower Project” and said a “Chinese company’s bus…was hit by a blast en route to the building site” in Khyber-Pakhtunkhwa.

The statement said the Chinese embassy had contacted the Pakistani military and unfamiliar and inside services and looked for steps to “reinforce security insurance for the Chinese residents, establishments and projects in Pakistan” and an intensive investigation of the episode.

“The Chinese embassy in Pakistan reminds Chinese residents, undertakings, and projects in Pakistan to stay on alert, pay close attention to the local security situation, take severe precautions, and quit going out except if necessary,” the statement said.

Asked about the issue during a regular unfamiliar service news preparation in Beijing, representative Zhao Lijian was equally gruff. He said China was “astonished to learn that the episode has caused heavy Chinese casualties”.

The Communist Party of China and the Chinese government attach high importance to the episode, and no exertion ought to be spared to “speedily discover what happened, lead inside and out an assessment of safety chances, and do our most extreme to guarantee the safety of Chinese workforce,” Zhao said.

“We have asked the Pakistani side to lose no time in leading a careful investigation, appropriately transfer and treat the injured, fortify safety efforts, eliminate security hazards, and guarantee the safety and security of Chinese workforce, foundations, and projects in Pakistan,” he said.

China will send a “cross-departmental joint working gathering” to Pakistan to assist with investigating the episode, Zhao said.

Hours before Chaudhry’s tweet, Pakistan unfamiliar minister Shah Mahmood Qureshi had maintained that the occurrence was an accident during a gathering with his Chinese counterpart Wang Yi uninvolved in a meeting in Uzbekistan.

“Preliminary investigation shows that it’s an accident and no background of fear-monger attacks has been discovered,” Qureshi was cited as saying in a readout from the Chinese unfamiliar service on his gathering with Wang.