Passengers leave the derailed MTR train on Tuesday morning. Photo: Screenshot of video from Sina Weibo

A train derailed at Hong Kong's Hung Hom Station on Tuesday morning, causing MTR services from the station to Mong Kok East Station to be temporarily suspended, local media reports said.

It was the first time a MTR carrying passengers has derailed in Hong Kong as unrest in Hong Kong entered their 15th week.

"We are concerned and saddened by the incident," Hong Kong Federation of Railway Trade Unions told the Global Times on Tuesday.

Some passengers speculated that a railway switch had somehow malfunctioned.

Others speculated that the derailment may be the work of radical protesters.

In early September, as rioters vandalized the entrance to MTR stations, bicycles were found being placed on train tracks and over electric cables near the train platforms, according to local media reports.

MTR officials have not yet determined the cause of the derailment, but quickly arranged buses for commuters to relieve congestion from New Territories to Kowloon.

Some radical protesters cheered the derailment, saying the MTR system is the "frontline" of their so-called non-cooperation movement, which aims to disrupt public transportation and hinder people from getting to work on time, according to online discussions on the social media platform LIHK.