On May 19, 1919, an eruption at Kelud killed an estimated 5,000 people, mostly through hot mudflows (also known as lahars). More recent eruptions in 1951, 1966, and 1990 have altogether killed another 250 people. Following the 1966 eruption, the Ampera Tunnels were built (top and bottom) on the southwestern side of the crater to reduce (not drain completely) the water of the crater lake and thus reduce the lahar hazard.