Dublin city council is investigating an alleged breach of planning permission at a concrete works in the East Wall area owned by Mexican cement giant Cemex.

The council issued a warning letter to the buildings materials company in July over activity at its concrete works at East Wall Road. A spokesman for the council said it had received correspondence from Cemex outlining the company's position and was now investigating the matter.

Cemex Ireland, established in 1965, is one of the largest building materials groups in the country and is one of CRH's chief rivals. Its parent firm is the largest building materials supplier in the world and the third-largest cement producer. The company operates at several sites in Dublin.

A spokeswoman for Cemex said it had made its position clear in correspondence with the council and would not comment further.