A MAJOR security alert has been sparked by illegal drone flights over Fawley refinery.

ExxonMobil, which runs the huge petro-chemical complex, has confirmed that the sightings are being investigated by Hampshire police and Britain's security services.

In a statement the company said unauthorised flights over the refinery were banned and posed a potential danger to staff.

The alert began last Saturday, when security staff at the refinery called the police after spotting "three or four" drones flying over the 3,250-acre site.

Workers at the complex say climate change protesters could be behind the unauthorised activity, which often takes place in the evening.

Fawley is the biggest refinery in the UK and one of the most complex in Europe.

Last night an employee said one of the drones usually appeared at around 8pm and circled the refinery for up to two hours, flying at an estimated height of 300ft.

He added: "It's massive. There are two lights on the object and they're quite far apart - it must be more than a metre wide.

"No-one really knows who is operating the drone or why they're doing it but some of us think Extinction Rebellion could be involved."

The ExxonMobil statement said: "There have been instances of unauthorised drone activity in the vicinity of the Fawley site in recent days.

"We are supporting the police and security services in their investigation.

"Unauthorised flights over the Fawley site are prohibited and pose a potential danger to staff on site."

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Image by Stephen Bath

The chairman of New Forest District Council, Cllr Allan Glass, added: "It means someone is interested in the refinery - and you never know what the reason for their interest could be.

"ExxonMobil's security is very tight. Hopefully if they're working with the police and the security services they'll get it nailed down pretty quickly."

A Hampshire police spokesman confirmed that officers were investigating.

He added: "We were first called at 7.48pm last Saturday after security at the Fawley refinery site reported they had seen three or four drones.

"Officers were deployed to the area and liaised with security.

"Further incidents were reported on Sunday, Monday and Tuesday. Enquiries are ongoing."

Cllr McEvoy, who represents Fawley, Blackfield and Langley, added: "Operating drones over the refinery could be dangerous.

"Unfortunately it's almost impossible to identify the people responsible for incidents such as this. They could be doing it for fun or mischief - or they could be doing it for other, more sinister reasons."