LIHUE, Hawaii >> Authorities are investigating the poisoning deaths of five pets in a Kauai subdivision but say it’s unclear whether they were intentional.

The four dogs and one cat were poisoned Jan. 25 in Kalaheo using paraquat, a highly toxic pesticide used to kill unwanted plants, state Department of Agriculture spokeswoman Janelle Saneishi said.

Kauai Humane Society field services supervisor Mana Brown said it’s unknown if the restricted-use pesticide was being used on a yard or if the animals came across it somewhere else.

"We’ve never seen anything like this before that was of this magnitude," Brown told the Garden Island.

Only licensed applicators can buy and use paraquat, according to the Centers for Disease Control and Prevention.

County spokeswoman Sarah Blane said the police department is working with the humane society to investigate.

Saneishi said the pets belonged to four separate owners, with two dogs belonging to one person. The animals came from within 10 houses of each other in the small South Shore neighborhood, Brown said.

An Agriculture Department inspector handed out flyers warning residents in neighboring communities to not let animals roam freely. "If you own a pet, please confine it to your property," the notice said.

Deliberate misuse of a pesticide is a violation of state pesticide law, which carries punishment of up to a year imprisonment, a $25,000 fine or both.