Local officials are on site to investigate a suspected arson attack on a bus in northwest China's Shaanxi Province on April 28, 2016. [Photo: xiancn.com]

Eight people were killed and five wounded on Thursday when a long-distance bus caught fire on a highway in northwest China’s Shaanxi Province.

Shaanxi police said in a statement that preliminary investigations indicated this is a criminal case and further investigations are underway.

Local media reports quoted police as saying the case involves hijacking and arson.

The attack occurred around 12:40 p.m. on the Lantian section of Yinfu Highway. Provincial and local officials are already on site investigating the case.