A method and device are provided for detecting the presence of slag in a shroud through which molten metal passed from a ladle to a tundish. An induced voltage generated at a receiving coil is compared with a defined voltage range. If the induced voltage has a value outside the defined voltage range, it is indicative of the presence of slag. The voltage range is defined in dependence of the flow of molten metal passing through the shroud. A casting plant is also provided.