Walmart’s Mexican subsidiary Walmex is facing fresh investigation by the US Congress, which says it has documents suggesting that the retailer may have engaged in tax evasion and money laundering.

This follows probes over allegations that the retailer bribed local Mexican officials to open stores more quickly.

Congressmen Elijah Cummings and Henry Waxman made the latest claim in a letter to Walmart chief executive Michael Duke.

Walmex said in a brief statement that it had no knowledge of any investigation by Mexican authorities into tax evasion and money laundering allegations.