The train, which started at 7.10 am from Mettupalayam near here, was stopped at Adderly around 8.40 am, when a big boulder and mud fell on the track, official sources said.
Further journey was cancelled as the rack and pinion section of the track was found broken and passengers were sent either to Coonoor by bus or taken back to Mettupalayam, they said.
Senior Railway officials and mechanics are attending to repair work, which is expected to be completed by evening, to facilitate the journey of the down train by then, they said.