Phillips 66 has moved to reassure customers that operations have not been interrupted at its Humber refinery after a walk out by contract workers.

The company released a statement saying: “On 10th November at approximately midday, an estimated 450 contract workers left the Phillips 66 Humber Refinery site in unofficial action.

“As of today, the workers have not yet returned to work. The safe and orderly operation of the facility has not been impacted by this action.”

Phillips 66 said it had been in dialogue with contractor management over the last week to discuss the workers’ concerns about on-site communications, and that it would continue to work with them to reach a satisfactory conclusion.

The statement added: “The workers have cited concerns over safety, which is the Humber Refinery’s number one priority. Following a recent vapour release on the 5th November, refinery management stopped all work for two hours and met face-to-face with every on-site contract company and their staffs to communicate what occurred and to reinforce Phillips 66’s commitment to safe operations.”

It said the vapour release occurred during routine maintenance and its emergency response team and an ambulance were called. As a precaution two contractors were taken to the local county hospital and they were later released to return to work.