Wichita ? The Wichita police department is investigating after about 30 egrets were found dead in a residential area.

The Wichita Eagle reports that egrets are protected by federal law and that it’s illegal to kill or injure the birds. People are also not allowed to harass or move them once they’ve nested.

The department has been working on the case with the Kansas Department of Wildlife and Parks. Authorities say they spent “all day” Wednesday investigating and that more information is likely to be released Thursday.

Egrets had been known to roost in a residential area a little more than a mile north of where the deceased birds were found, sometimes irritating residents. But most of the trees they used to roost were bulldozed last year.