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Ringdown detection methods like Kalman filter and Prony analysis have been developed to aid transmission operators to track lightly-damped inter-area oscillations. Kalman filter detection is dependent on a priori system knowledge and is designed to monitor the dominant mode. The objective of this paper is to extend Kalman filter to track multiple modes. Thus, extended complex Kalman filter (ECKF) based procedure is formulated and assessed. While retaining the recursive Kalman filter engine, the proposed method redefines the state variable representation to directly estimate the modal parameters instead of using the existing polynomial rooting approach. It also integrates Hankel singular value decomposition (HSVD) to provide better estimates of the initial conditions.