* Toxicologists found "huge increase" in chemicals
* Waters near Louisiana are most affected
* Congressman wants probe into Federal oil spill report
NEW YORK, Sept 30 (Reuters) - University researchers said on Thursday they recently found alarming levels of cancer-causing toxins in an area of the Gulf of Mexico affected by BP's (BP.L) oil spill, raising the specter of long-lasting health concerns.
Oregon State University (OSU) researchers found sharply heightened levels of chemicals including carcinogens in the waters off the coast of Louisiana in August, the last sampling date, even after BP successfully capped its runaway Gulf well in mid-July.
Near Grand Isle, Louisiana, the team discovered that polycyclic aromatic hydrocarbons (PAHs) -- which include carcinogens and chemicals that pose various risks to human health -- remained at levels 40 times higher than before the area was affected by the oil spill.
The compounds may enter the food chain through organisms like plankton or fish, a researcher said.
"In a natural environment a 40-fold increase is huge," said Oregon State toxicologist Kim Anderson, who led the research. "We don't usually see that at other contamination sites."
The PAH chemicals, which are often linked to oil spills, are most concentrated in the area near the Louisiana Coast, but levels have also jumped 2 to 3 fold in other spill-affected areas off Alabama, Mississippi and Florida, Anderson said.
As of last month, PAH levels remained near those discovered while the oil spill was still flowing heavily, Anderson said. The team will continue to sample for chemicals in months to come.
Although BP has sealed its well, experts are still cataloging the environmental and health hazards left in the wake of the spill. Scores of research teams, including Anderson's, are working with Federal Superfund grants to measure how the spill affected the environment.
Also on Thursday, Arizona Congressman Raul Grijalva told Reuters he would press for a congressional investigation into whether estimates of the oil spill volume and its related environmental risks were misrepresented in a federal report from early August.
BP's ill-fated Macondo well spilled a total of up to 4.9 million barrels before it was capped, the report said. But it also suggested that most of the oil had been dispersed naturally or removed by clean-up efforts at the time.
Grijalva, who chairs a subcommittee that oversees some wetlands damaged by the spill, said it was unclear whether the Federal report was peer-reviewed and whether its estimates remain accurate.
"I don't want to let BP off the hook, and my suspicion is that the numbers may be wrong and that the oil is still a danger," Grijalva said in an interview.
BP representatives were not immediately available for comment.
(Editing by David Gregorio)