The Rajasthan Police have arrested 31 people involved in the theft of nearly 50 million litres of crude oil worth Rs 49 crore from a Cairn India plant in Barmer district, PTI reported on Monday. The racket is believed to have gone on undetected for nearly six years.

The Cairn India oilfield in Barmer is India’s largest onshore block. It produces about 1.75 lakh barrels of oil per day.

On July 14, the company’s legal officer had filed a complaint at Barmer’s Nagana Police Station against tanker operators after suspecting a scam. The racket came to light after the Rajasthan Police arrested 25 people last week for their involvement in the network of oil smugglers. The police said two of the five compartments in tankers used to transport water were filled with crude oil.

The crude was then allegedly sold to two factory owners, Gautam Singh and Bhoor Singh, who paid Rs 7.50 per litre to the owner of a tanker company. These factory owners then sold the product in various states, including West Bengal, Gujarat and Delhi, reported The Times of India.

“Seventeen drivers involved in the syndicate have been arrested,” Superintendent of Barmer Police Gagandeep Singla told PTI. At least seven accused were employees of Cairn India.

The accused said nearly 15,000 litres to 20,000 litres of crude oil worth Rs 3 lakh were stolen every day. This cost Cairn India at least Rs 11,000 crore in losses every year. The company said it was cooperating with the police in the investigation.