Karachi: Pakistan's Foreign Office expressed its condolences to the families of the Chinese and Pakistani workers who lost their lives in the bus blast on Wednesday, saying that authorities are providing all possible assistance to the injured and investigations into ascertaining the cause of the incident are underway.

The FO in a statement prayed for the quick recovery of the injured.

"This (Wednesday) morning a bus carrying Chinese workers in Khyber Pakhunkhwa Province, plunged into a ravine after a mechanical failure resulting in leakage of gas that caused a blast," said the FO statement released shortly after the incident. "Further investigations are underway."

Bus blast near Dasu project kills at least 13, including 9 Chinese

According to preliminary reports, nine Chinese nationals and three Pakistanis lost their lives.

"Chinese workers and accompanying Pakistani staff were proceeding to their work place for an ongoing project. The local authorities are providing all possible assistance to the injured," added the statement.

"The Ministry of Foreign Affairs is closely in contact with the Chinese Embassy for coordination and facilitation.

"The Government and people of Pakistan extend sincere condolences to the families of Chinese and Pakistani workers who lost their lives in the incident. We also pray for quick recovery of the injured.

"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."

Earlier, a senior administrative officer of the Hazara region told Reuters that the bus was carrying more than 30 Chinese engineers to the site of the Dasu dam in Upper Kohistan.

The Dasu hydroelectric project is part of the China-Pakistan Economic Corridor (CPEC), a $65 billion investment plan under Beijing's Belt and Road Initiative that is aimed at connecting western China to the Gwadar seaport in southern Pakistan.