As many as 34 small holes had been drilled into the track with 14 of them on one side and another 20 on the other, police said.
Railways and Kerala police have begun investigations. A police team led by Kozhikode Police Commissioner A V George inspected the track and drew up a preliminary report.
"We have not reached any conclusions. We have begun an investigation," George told reporters.
According to police sources, the holes could have been made using a sound-proof driller as people living on either side of the track said they did not hear any noise.
The holes came to the notice of the track maintenance workers after several trains passed through the spot till the afternoon. The necessary repair works to plug the holes were carried out.
Railway sources said these holes would have rendered the tracks unsafe in due course had it gone unnoticed for a few days.