The South Western Railway (SWR) zone has begun investigation to identify a duo who impersonated travelling ticket examiners (TTE) and demanded fare from migrants in a Shramik special train bound for Uttar Pradesh, an official said on Tuesday.

"Investigation is on. First the persons need to be identified," railway zone spokesperson told IANS.

The incident happened on Sunday in a special train packed with migrant labourers and departing from KSR Bengaluru station to Gorakhpur in Uttar Pradesh.

The impostors started demanding Rs 905 from the passenger as fare to their destination.

Incidentally, the matter came to light when an NGO tweeted about the incident, tagging some railway officials and the city police commissioner.

One of the passengers called the NGO and complained about the matter. He told them that the impostors threatened to offload them from the train if they do not cough up the fare.

The fake duo was seen wearing uniform similar to a TTE.

Both of them tried their trick in a few coaches but none of the passengers gave them the money, according to the official.

"No one paid, I understand," said the official.

On coming to know about the matter, the railway authorities checked the train and also announced at stations enroute about the matter to the migrants in the train.

The train was also halted at Hindupur in Andhra Pradesh's Anantapur district where the railway police took the statement of the migrants.

The railway zone is running daily Shramik special trains to multiple northern and eastern states and has already ferried more than 3 lakh people.