This paper firstly presents an electromagnetic induction tomography (EMT) system of an 8-coil array operating at a single excitation frequency, aiming to reconstruct images with real data measured from hot trial tests. The results were consistent with video recordings of an exposed section of the steel flow passing through a submerged entry nozzle, in terms of flow size and positions, providing a good representation of the steel flow profile changes during trials. This paper then presents the latest development of a multiple-frequency electromagnetic induction system for steel flow visualisation. The system is designed based on a commercial data acquisition board, which can provide three sinusoidal signals with target frequencies for excitation simultaneously. The paper reviews the new hardware electronics and software that is implemented based on a frequency division multiplexing approach. Experimental results show that the system is able to identify a variety of test samples, even in a case when a small metal rod moves inside a big rod of the same composition. Instead of imaging the cross-section of the steel flow profiles, the current system is developed for checking signal levels at different operation frequencies, which are of more interest for industrial use. Nevertheless, the work demonstrates a significant step forward to develop a multiple-frequency EMT system for future industrial process applications.