Air quality in Singapore improved significantly to "moderate" pollution levels on Saturday, as Indonesian planes waterbombed raging forest fires and investigators scrambled to determine the cause of one of Southeast Asia's worst air pollution crises. Indonesia's environment minister said eight domestic firms were suspected of being responsible for the blazes on Sumatra island that blanketed neighboring Singapore in record levels of hazardous smog. The parent companies of the Indonesian firms included Malaysia-listed Sime Darby and Singapore's Wilmar Group. A senior presidential aide on Friday also blamed units of Jakarta-based PT Sinar Mas Agro Resources and Technology (SMART) and Asia Pacific Resources International (APRIL) for the fires. "We will take legal action whoever they are," Environment Minister Balthasar Kambuaya told reporters. "Any companies from Indonesia , Malaysia or Singapore, they will be legally processed." But Indone