Hundreds of workers at an oil refinery have voted to continue an unofficial strike in a dispute over safety.
Engineering construction employees at the Humber Refinery in North Lincolnshire decided at a mass meeting not to return to work.
The refinery, owned by Phillips 66, processes barrels of crude oil into petrol and diesel.
Sources said around 450 workers were involved in the row, following a gas leak which injured two men.
The GMB union said it was aware of a health and safety issue on the site.
The workers will hold another mass meeting today to decide their next move.
A company statement said: "On November 10 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 has been in ongoing dialogue with contractor management over the last week to discuss the workers' concerns over onsite communications, and we will continue to work with them to reach a satisfactory conclusion.
"The workers have cited concerns over safety, which is the Humber Refinery's number one priority. Following a recent vapour release on November 5, refinery management stopped all work for two hours and met face-to-face with every onsite contract company and their staffs to communicate what occurred and to reinforce Phillips 66's commitment to safe operations.
"We will continue to operate in a safe manner as we work toward a resolution."
GMB national officer Phil Whitehurst said: "Following a major stoppage of work we have been advised that there is a major health and safety issue on the site.
"GMB has been refused access to the site in order to resolve what has been described to us as a major hazard.
"We urge the company to allow the union on to the site to try to resolve the issue as quickly as possible for the safety of workers and the public."