Testing by the Food and Drug Administration found that 6 percent of canned light tuna samples contained large amounts of mercury, a toxic metal that can cause learning disabilities in children and neurological problems in adults.

The findings are significant because the government has repeatedly stated that canned light tuna is low in mercury and a good choice for pregnant women and young children.

FDA also found high mercury levels in samples of Chilean sea bass, which is often sold in high-end restaurants. Previously, the FDA had tested only one sample of the fish. And high levels were detected in big-eye tuna, a species often sold as ahi tuna and served in sushi.

No federal warnings exist for either fish, even though the average mercury level detected in the FDA tests was above the average in albacore tuna, which the government tells pregnant women and young children to limit eating.

In all, the FDA released testing results for more than 25 kinds of fish, sampled between 2001 and 2005. The findings were not released until now partly because the analysis wasn't complete, the agency said.

While a few species, such as tuna and Chilean sea bass (also known as Patagonian toothfish), were tested frequently, many were not. Only one catfish, one flatfish, two mahi mahi, four crabs and seven sardines were tested, the FDA data show.

More online

* Read all of the FDA data at:

http://www.cfsan.fda.gov/~frf/seamehg2.html