The two levels of controls were a gauge that failed to operate and an independent high-level switch (IHLS) which was not operational. The gauge was previously maintained in august of that year when it stuck but maintenance people could not explain why it had failed again. The independent high-level switch was not operational due to lack of a lever that was to maintain it in an operational state. This was however not reported by the maintenance crew, which led to all the confusion (Mannan 2006).