A fire during a routine maintenance drill at Saudi Arabia’s United Petrochemical Company’s plant in the industrial city of Jubail has killed 12 workers and injured 11, according to state news agency SPA.

The fire was small with smoke inhalation causing the deaths, said the report.

Although the cause of the fire remains unclear, Saudi Arabia has come under pressure in the past regarding health and safety standards.

United Petrochemical Company is a subsidiary of state-owned Saudi Arabia Basic Industries Corporation (Sabic), which is currently diversifying its sources of finance and expects export credit agencies (ECAs), Islamic finance and capital markets to play a larger role in its plans for the future.

Jubail has been hailed as a great opportunity to fully diversify Saudi Arabia’s economy.