HOULTON, Maine — The Houlton Humane Society is in the middle of a major upheaval following the abrupt resignation Tuesday evening of its long-time executive director Heather Miller.

Houlton Police Chief Joe McKenna said Wednesday that his department has received and is investigating multiple complaints from the public about the shelter, including the alleged death of a dog found on the property.

“I don’t know if that [death of a dog] is going to be a criminal act because the statute is very vague,” McKenna said. “All I can say is we do have an open investigation about the shelter.”

McKenna said that the state’s Animal Welfare office had been notified and is involved in the investigation. The chief added that officials at the shelter have been cooperating fully with the investigation.

Monica Gray, president of the board of directors, confirmed Wednesday that Miller had resigned the previous night. Gray said Ramona Conrad, who has been on the board for about a year, has been chosen as the new interim executive director for the shelter.

“I cannot comment on anything involving Heather,” Conrad said. “I can say that we are looking into it and will be releasing a statement in the near future.”

Gray said she too could not comment on the reasons behind the resignation because of the ongoing police investigation. She did say that no employee had been fired from the shelter for leaking information connected to the investigation.

Miller, who declined to comment on Wednesday, has been the shelter’s executive director since 2009. Prior to that, she worked part time as a medical assistant at the shelter, administering medicine to animals, and also did secretarial duties.