Cincinnati Police are investigating the circumstances surrounding a four-year-old boy entering a gorilla's exhibit at Cincinnati Zoo and the animal being shot dead to protect the child.
They hope to learn what transpired with the death of Harambe before talking with prosecutors about whether charges are warranted, Hamilton County prosecutor Joe Deters' office said.
Some critics have said the boy's parents should be charged with child endangering, while others want the zoo held responsible for the death of the 17-year-old western lowland gorilla.
The boy was released from hospital later on Saturday and his family has said he is "doing just fine" at home.
Tanya Espinosa, a spokeswoman for the US Department of Agriculture (USDA)'s animal and plant health inspection service, said there was not an investigation open yet but that it would be looking into the incident for any violations of the Animal Welfare Act.
The executive director of a Cincinnati-based animal rights organisation is calling on the USDA to fine the zoo.
"The (zoo's) barrier obviously isn't sufficient to keep the public out," said Michael Budkie, of Stop Animal Exploitation Now.
"Otherwise, Harambe wouldn't be dead."
A routine inspection from April 4-7 that included the gorilla area did not find any violations, another report said.
Inspections in 2014 found several issues including the need to repair areas where monkeys and horses were housed and a camel that appeared to be badly bothered by flies.
Zoo director Thane Maynard said the zoo has received a lot of support from visitors and animal experts since Saturday.
Maynard said the zoo remains safe for its 1.6 million annual visitors, but a review is under way to determine any improvements that can be made.