China Railway Corp has responded to reports that it used substandard cables that were prone to catching fire and releasing toxic gases when ignited.

The authority said it always put transport safety first and a team had been formed to inspect and replace all the problematic cables provided by Shaanxi Aokai Cable Co, People's Daily reported on Friday.

Affected railway lines included those connecting Baoji, Shaanxi province to Lanzhou, Gansu province; Xi'an, Shaanxi, to Chengdu, Sichuan province; Chongqing to Guiyang, Guizhou province; and Lanzhou to Chongqing.

Three metro lines in Chengdu were also affected, according to Chengdu Rail Transit.

"We always put transport safety first and cannot bear any security risks," China Railway Corp was quoted as saying by People's Daily.