The engine of train no. 12623 mail superfast express from Chennai to Thiruvananthapuram seized up after it left the station here and reached the nearby tunnel around 7.35 a.m. on Tuesday.
As it got stranded on the single line, several trains were held up at stations such as Changanassery, Ettumanur and Thiruvalla for two-and-a-half hours.
The line was cleared after an engine was brought from Ernakulam and connected to the stranded train at 10 a.m. Many passengers had got off the train by then and took buses to their destinations.
Railway authorities said the engine started malfunctioning soon after the train left the Tripunithura station.