State health officials have now determined what caused three Iowa Falls convenience store employees to become seriously ill while at work Tuesday.

According to John Mchugh, director of corporate communications for Kwik Star incorporated, the problem was caused by oven cleaner that was not completely cleaned up before the store’s oven was used again.

The affected employees were sent to the hospital, and all employees were reported as having returned to normal health status as of Wednesday.

(By Brent Weithorn, KFJB, Marshalltown)