The level of mercury in the blood of autistic children is no different than that of their typically developing peers, according to new research that takes aim at the theory held by some parents that one trigger -- mercury in vaccines -- causes autism.

Several studies have ruled out that vaccines cause autism. Nevertheless, the issue sparks controversy in some circles at just the mention of a possible link.

The new study by researchers at the University of California Davis' MIND Institute, looks directly at blood-mercury levels and finds they are virtually no different a group of 452 children 2 to 5-year olds, 249 of whom were diagnosed with autism. The study examined a wide range of sources of mercury in the children's environments, from dental fillings to fish consumption. The research, published in the journal Environmental Health Perspectives, comes from a long-range study to identify causes of autism, a wide spectrum of disabilities marked by impaired communication and social interaction.

It's important to note that while the study is among the first to examine the blood mercury levels of children with autism, researchers cautioned that they did not probe whether mercury is a factor in the cause of autism.

Still, researchers point to it as evidence that a host of research is necessary to identify what is likely a complex web of causes for a very complicated set of neurobiological disorders.