The female crocodile was found floating next to Florida Bay mangroves in Lower Matecumbe Sunday, The Miami Herald reported.
Investigators said it was the same crocodile wildlife officers relocated in April after it laid eggs in the Tollgate Shore neighborhood.
Carli Segelson, a spokeswoman for the Florida Fish and Wildlife Conservation Commission, said she could not say how the crocodile died, but "obviously, it was suspicious to the point where we felt it needed to be investigated."
The FWC and Humane Society have offered up to $6,000 for information leading to an arrest and conviction in the case. Killing a crocodile is a felony in Florida.