Around 200 workers have walked out of ExxonMobil’s petrochemical plant at Mossmorran in Fife over health and safety issues, according to a union.
Unite claims health and safety warning signals and procedures are not in “full working operation” at the site.
It also said the workers, from three separate contractors, were not told of any contingency safety plans in place.
ExxonMobil said the Fife Ethylene Plant fully complied with its approved site safety standards and procedures.
ExxonMobil said fewer than 100 contractors were involved in the action and it was having “no impact on operations”.
Unite said it had received reports of alarm systems not working in areas of the petrochemical plant over the last year.
These are required in the event of any leakages, blasts or exposure to hazardous materials and chemicals.
The union also said there were various recorded incidents at the plant over safety, pollution risks and environmental damage.
It said ExxonMobil and the contractors involved were refusing to pay worker wages following the walk out.
Unite’s general secretary Sharon Graham said: “Unite will robustly defend the legal right of our members to withdraw their labour over health and safety concerns at ExxonMobil’s Mossmorran plant.
“It is completely unacceptable that the company and the various contractors on site are refusing to pay our members their wages.
“This is a legal duty and not open to interpretation. Our members will be receiving their union’s unflinching support.”
The union has called on the Health and Safety Executive to investigate.
Workers at Mossmorran previously walked out over safety concerns in 2020.
ExxonMobil said it was aware of “unofficial action instigated by a small number of individuals” at the site.
A spokesperson added: “There is no impact on our operations, which continue as normal.
“Fife Ethylene Plant operates in full compliance with approved site safety standards and procedures.”