Arlington Park announced it is examining the late action on the winner of the second race on June 28.
In a statement, track president Cliff Goodrich said. "Once more information has been obtained and reviewed, we will make it available to the public."
The odds on the winning horse Rainy Day Rules were reportedly 9-1 at post time before dropping to the final odds or 5.90-1 once the pool was finalized as the race was being run. Rainy Day Rules paid $13.80, $8.00 and $6.40.
Arlington, like the vast majority of racetracks in North America accept wagering until the bell rings and the horses leave the starting gate. It takes approximately 20 seconds to accumulate and verify all pools that are received from off-track locations. Changes in the odds once the race starts can occur when those late pools are included.