The quarantine that was ordered on Saturday when the two horses showed signs of Streptococcus equi, or strangles, remained in effect Tuesday as a precaution while test results were awaited, according to Jeff Smith, the park's general manager of racing. The situation was not expected to affect the next live racing event on Wednesday evening, he said.

The highly contagious respiratory infection causes swelling in horses' lymph nodes, head and neck, but is rarely fatal to them and presents no threat to humans. Bacteria are transferred by contact from horse to horse and can be carried on clothing of jockeys and trainers.