Two men arrested on suspicion of the theft of thousands of litres of fuel believed to have been stolen from one of the UK's main underground oil pipes which runs through Wiltshire have been released on bail.
The suspects, aged 32 and 34, were arrested after a large quantity of diesel was discovered in a warehouse in West Wellow, on the Hampshire and Wiltshire border.
It is understood that detectives are investigating whether the 30,000 litres of fuel was extracted from a pipeline running from the Esso refinery at Fawley in Hampshire.
The two men arrested in Salisbury have been released on bail by Hampshire Police until July 10 pending further inquiries.
The Midline pipeline was built in the 1980s and runs underground, carrying fuel through Wiltshire to the Midlands, including Birmingham International Airport.
Officials from the Environment Agency and health and safety experts have attended the crime scene to ensure the safety of the area.
An Esso spokesman said: "Esso is assisting Hampshire Police with their inquiries following the discovery of a store of fuel in the Romsey area.
"Early indications suggest that the fuel may have come from a nearby Esso pipeline. Investigations continue into whether this is the case.
"Esso is committed to the very highest standards of safety. The pipeline has therefore been closed down and our specialists are working to check it and, if necessary, effect any repair.
"We will not resume operations of the pipeline until this work is complete."
A Hampshire Police spokesman said: "Police launched an investigation after a large quantity of diesel was found in an industrial storage unit at West Wellow.
"Lines of inquiry include establishing the exact amount of fuel stolen and examining the suspected sophisticated method used in this alleged theft.
"The discovery was made by the unit's owner at around 7.30pm on Thursday. It is believed to have been illegally obtained.
"The exact quantity and circumstances surrounding the accumulation of fuel are central to the investigation, and detectives are focusing on identifying those responsible.
"The fuel is stored safely and securely and is being retrieved by engineers from the nearby Esso refinery.
"The investigation, led by Lyndhurst CID, is still in its early stages and this is all the information we are able to release at this time."
An Esso spokesman confirmed that a tapping device had been found on the pipeline and efforts were being made to repair it.
He said: "A tapping device has been found on the Esso Midline pipeline that transports fuel from the Fawley Refinery, Hampshire, to Birmingham Fuel Terminal.
"This follows the discovery by Hampshire Police last week of a store of fuel in a barn at West Wellow in Hampshire.
"The Esso Midline pipeline is secure and there has been no leak of product. The pipeline was closed as a precaution following the discovery of the fuel store.
"Esso is committed to the very highest standards of safety and our specialists are now working to remove the tapping device, and repair and test the pipeline and restore it to normal operations as soon as possible.
"Interim alternative supply arrangements are in place and we do not anticipate any impact on our retail customers.
"We continue to help Hampshire Police with their inquiries."