Despite being not directly linked to Titas Gas Transmission and Distribution Company Limited, they would go to households to assist linemen and supervisors of the national gas distributor.

Having worked on a daily basis for a long time, they learnt how to fix different issues regarding gas connections. They also somehow got access to the Titas head office in the capital.

At one point, they stole from the office files with details of over 500 subscribers, who were failing to pay bills timely or had problems in their connections. They then carried out fake raids on many of those households identifying themselves as Titas employees.

They took a huge amount of money from those subscribers illegally. They would charge extra to fix gas lines or provide them with illegal connections in different areas of Dhaka.

These criminals are members of three to four syndicates, who include several current and former employees of Titas.

The Criminal Investigation Department (CID) claimed to have gleaned the information from three members of one such syndicate. The three have been arrested recently.

"Because of these syndicates, the government is losing a huge amount of money in revenue," Mohammed Kamruzzaman, special superintendent of CID (Dhaka Metro), told The Daily Star yesterday.

The arrestees are: Habibur Rahman alias Anowar, 24, Saiful Islam, 32, and Nazrul Islam, 32. The CID said they were involved in the fraud for at least five years.

A CID team also recovered ID cards of Titas employees, a file with details of 500 Titas subscribers and money receipts from the arrestees.

Kamruzzaman said they made the arrests on June 7 following a complaint by a Titas subscriber in the capital's Moghbazar area.

The subscriber got gas connections to 32 flats in 2016. He, however, was never asked to pay bills by Titas, which stopped providing new connections immediately after the subscriber had it.

Suddenly, last year, members of a syndicate contacted him and asked him to pay a huge amount of money. At one point, the gas connections to the flats were cut off.

In January this year, the syndicate members, wearing Titas ID cards, appeared before the subscriber's building with a pick up and reconnected the gas line after they were paid Tk 1 lakh, said Kamruzzaman.

The syndicate members then asked for Tk 19 lakh from the subscriber, promising him that they would settle all the issues over the payment of due bills. The subscriber then paid Tk 15 lakh to arrestee Habib and his accomplices.

Taking the money, the criminals, however, stopped receiving the subscriber's phone calls. 

In May, the subscriber went straight to Titas office, where he came to know that he was defrauded and that Titas had nothing to do with the syndicate, said the CID official.

"The victim then came to us. A case was filed with the Hatirjheel Police Station," Kamruzzaman said, adding that law enforcers were investigating the matter.

The CID official said the syndicate members had been working with Titas employees since 2014. They have machines needed to fix and set up new gas connections.

"We have already got the names of some former and current employees of Titas by interrogating the arrestees. We're now verifying the information," he said.

"We would definitely interrogate those officials if we find their links with the crime. We will write to the Titas authorities soon," he said.

Each syndicate, which has eight to nine members, is involved in giving illegal connections in Dhaka's Demra, Banani, Mohakhali, Kakali, Keraniganj and Uttara areas, said the official.

"We are now conducting drives to arrest the absconding members," Kamruzzaman said.

He, however, refused to disclose the names of the Titas employees, saying that the investigation was still underway.

Ali Iqbal Md Nurullah, managing director of Titas Gas, told The Daily Star that they were yet to be communicated by the CID. He said they would cooperate with anyone who would come to them with specific complaints.