One person died and two others were injured after a collision of test trains on a metro line under construction in Xi'an, capital of northwest China's Shaanxi Province, according to the municipal authorities on Saturday.

The authorities said that the accident on Line 10, which is being constructed, happened at 11:50 p.m. Thursday, due to "improper operation by field test personnel." Test vehicles had a rear-end collision, resulting in the casualties and vehicle damage.

The cause of the accident is still under investigation.