The Essar oil refinery has apologised for the release of an odour that sparked widespread concern in Ellesmere Port and Neston on Friday night (March 2).

Fears about a gas smell prompted 150 calls to the Cadent (formerly National Grid) hotline but engineers were left scratching their heads despite working until 4am.

Police even became involved after receiving multiple calls about ‘a strong gas-like smell’ .

Reports on social media suggested many people could smell something in the air with advice apparently given over the phone for people to keep their windows and doors closed.

Now Essar has admitted it caused the stink but claims the odour was ‘not harmful’ although the company has not revealed the exact nature of what escaped to the atmosphere.

National Grid engineers worked until 4am trying to discover the source of gas-like odour that came from Stanlow.

A spokesperson said: “Stanlow refinery is currently shut down for a major maintenance turnaround. During pre-commissioning work on a particular unit, a release of odour was reported on Friday night and was addressed at the time. We assure the public that the odour was not harmful. We apologise to anyone who was exposed to an unpleasant odour.”

Essar has acknowledged it does not have a system in place for informing the public about occurrences such as the incident on Friday night.

The Chronicle is awaiting a response from the Environment Agency.

■ In February 2017 National Grid received more than 100 calls to its emergency service number due to a mystery gas smell.

Businesses at Cheshire Oaks and nearby householders, including from the Stanney Oaks estate, could smell what was thought at the time to be a gas leak from about 10pm. The source of the odour could not be traced.