No casualties were reported. The train driver had failed to notice the boulder that had fallen on the track, a Southern Railway release said.
The train pushed the boulder to some distance after which two engines and a compartment derailed, disrupting traffic on the route. The train was later brought back to Subrahmanya Road station and to the Central railway station here.
The train would be diverted via Kannur, Shoranur, Palakkad and Erode to Bengaluru, the release said.
Train number 16515 Yeshwantpur-Karwar Express scheduled to leave Yeshwantpur today was also cancelled, the release said.