Five "haze-proof" locomotives, which were designed to prevent haze-induced electric problems, have been sold to China Railway Corp, a rail-vehicle manufacturer announced.

The HXD3C trains, produced by a subsidiary company of the China CNR Co Ltd, are able to work effectively even in foggy and hazy weather, China CNR said in a statement released on its website on Wednesday.

Heavy-metal particles suspended in hazy air can affect electric devices on top of the locomotives and even paralyze the trains' engine system, the statement said.

The company said that in the past, when air pollution was not as bad, it was easy to clear dust from the top of the trains using blowing machines. However, with the worsening pollution in recent years, cleaning the trains has become more difficult.

The company got an order for 50 haze-proof locomotives from China Railway in the latter half of this year.

The company's engineers have been to Hebei province and the municipalities of Beijing and Tianjin, where the air pollution is heavy, to test and improve the locomotives' capabilities, the company announced.

When the five locomotives will go into service is unclear. China Daily's phone calls to China Railway and the CNR went unanswered on Thursday.

On Jan 16, a train bound for Handan, Hebei province, had its electricity cut off when it arrived at a station in the morning. The railway authorities found that the failure was caused by the hazy weather, since the floating particles stuck to the electric networks, Hebei Youth Daily reported.

Power was resumed after the locomotive was replaced. No passengers were injured, the report said.