Two horses that raced at Lone Star Park April 13 tested positive for erythropoietin (EPO) antibodies, which brings the total number of horses to test positive in Texas this year to eight."We're very concerned," Lone star general manager Jeff Greco told the Dallas Morning News. "and will work with the regulators to ensure the integrity of our racing.Earlier this year, six horses at Sam Houston Park tested positive for EPO antibodies and 15 cases were found in Illinois. New York also has had an unspecified number of positive tests.No disciplinary action will result from the positives because current testing can only find EPO antibodies, not the drug itself. Additionally, there is no confirming method. The Texas Racing Commission recently begun EPO testing to try and figure out how widespread its use is.Another problem with EPO testing is the drug, which stimulates production of red blood cells, can remain in a horse's system for months. Thus, the EPO could have been administered by a prior trainer or owner.A Texas Racing Commission official said the horses' current owners would be notified of the test results by letter.