SINGAPORE, Nov. 1 -- Five Singapore-registered companies potentially linked to fires in Indonesia that contributed to transboundary haze have agreed to independent assessments of their operations and supply chains, as Singapore intensifies efforts to establish corporate accountability for cross-border pollution.

The companies include some of the region's biggest agribusiness players, whose complex ownership structures and plantation operations have come under scrutiny over fires that have repeatedly blanketed parts of South-east Asia in smoke.

Singapore's National Environment Agency (NEA) said yesterday that representatives from Wilmar International, Golden Agri-Resources, APP Company, APP Company (China) and Indofood Agri Resources had...