The sole rail investment and operation company in Chengdu reported on Wednesday that the city's subway system has used electric cables from a company that provided substandard products to the Xi'an metro system.

Three metro lines in Chengdu, capital of Sichuan province, including one already in operation, were found to have used the electric cables, according to Chengdu Rail Transit.

The two major contractors of Chengdu's metro system, China Railway Group Ltd and Power Construction Corporation of China, apologized to the public in a statement released on Wednesday for using the potentially dangerous cables and vowed to replace them all to reassure the public.