The aim of this paper is to exploit grain price data to detect the warning signs of looming food crises in Mali, Burkina Faso and Niger. Firstly we identify which markets play a leading role at the national and regional level. The second step consists of identifying crisis periods and characterizing price movements during the period proceeding a crisis. This analysis leads to the identification of early warning indicators whose relevance is tested using panel data qualitative choice models. The results show that monitoring price movements on "leading markets" during crucial periods of the year can help in forecasting future crises.