At least two rural primary school students died and another 20 were injured after a horse-drawn wagon they were aboard collided with a truck in southwest China's Yunnan province on Wednesday, local authorities said.

The wagon was carrying 24 students from a primary school in a local village when the accident took place at about 12:45 p.m. on a highway in Qiubei county, the county government announced in a statement.

One student was killed instantly, and another died in hospital, the statement said.

An investigation into the cause of the accident is underway, it added.