GUIYANG, Feb. 28 -- A fire on a bus that killed six was a criminal act and a suspect has been identified, police in southwest China's Guizhou province confirmed.

The fire was started at around 1 p.m. Thursday as the bus was passing a primary school in the northern part of Guiyang city. The fire spread quickly and many people simply did not notice the emergency hammers to smash the windows, according to survivors.

A four-month-old boy was among the six dead.

The suspect is yet to be arrested and a further investigation is underway.

The 35 injured, including one in critical condition, are being treated at local hospitals.