BLACK smoke is billowing into the sky from Fawley oil refinery with two flares lit at the facility.

It comes after ExxonMobil apologised for noise last weekend when it restarted equipment.

The corporation says the use of its flares is safe and approved - and can be used to purge units of hydrocarbons.

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They are also a safety system. "Our flares are Fawley's ultimate safety mechanism, operating quickly and safely to manage operational upsets when we need to release pressure and hydrocarbons from our units," a statement on the website said.

A previous statement said: "I want to directly apologise for any noise disturbance caused by the essential work conducted on our site over the weekend.

"As we communicated in advance, this was associated with the re-start of a major process unit – our Cat Catalyst Unit.

"The process requires us to use our flares into which we inject steam to help ensure that the flare is not smoky. Unfortunately, it is this process that caused the increase in noise.

"We had anticipated the completion of the re-start during Saturday, but it took us slightly longer to bring the unit up to its operating temperatures and throughput.

"While we had to maintain the controlled use of the flares during this time, our team worked hard to manage the volume of steam to help reduce noise where possible. We exited the flares at around 11am yesterday.

"Once again, we are sorry for any disturbance caused to your weekend and we will take away any learnings that will help us reduce impact in the future."