The Brazos County Sheriff's Office is investigating the deaths of the 27 horses at Carousel Acres.
The College Station equestrian center's owner, Brad Raphel, contacted sheriff officials two weeks ago, saying he believes the horses were intentionally killed.
"He suspects that the horses were individually poisoned," Chief Deputy Jim Mann with the Brazos County Sheriff's Office said. "Once somebody makes the complaint like that, we go ahead and write up a case and assign an investigator to it."
Sheriff's officials say they have interviewed several people in regards to the incident, but have found nothing suspicious.
The investigation is on-going.
On July 16, 24 horses mysteriously dropped dead in the Carousel Acres' pasture. Three more later died under care at Texas A&M University.
Data released in July showed the presence of toxic phosphine gas in the dead horses' stomachs.
The Department of Agriculture is still investigating the incident and will release toxicology reports later this month.