The police watchdog has said there is “an indication of misconduct” by three radio operators at Greater Manchester police prior to the murder of 18-year-old student Ellen Higginbottom.

The A-level student was reported missing on the evening of 16 June after failing to return home from Winstanley College in Wigan. Officers began a search, describing the teenager’s disappearance as “extremely out of character”. Higginbottom’s body was found at the nearby Orrell Water Park in the early hours of the following morning.

Mark Buckley, 52, was jailed for life for her “sexually motivated” murder on 14 September. A postmortem examination showed that the teenager, who aspired to be a vet, died from multiple wounds to the neck.

The Independent Police Complaints Commission (IPCC) investigation, which is ongoing, is looking at the response by Greater Manchester police to the missing person report and their actions up until the discovery of Higginbottom.

The watchdog said that, based on the evidence collected so far, their lead investigator had decided there was an indication of misconduct by three radio operators and that the individuals concerned had been notified. Interviews with key police witnesses will take place over the coming weeks.

The IPCC delegate Andy Riley said: “The investigation is making good progress. I would like to thank Ellen’s family for their continued assistance with this investigation. We are providing them with regular updates, and our thoughts remain with them as we continue our work.”

Misconduct notices inform officers or police staff that their conduct is under investigation. Greater Manchester police said it would not be appropriate for them to comment before the IPCC investigation had concluded.

Sentencing Buckley in September, David Stockdale QC, the honorary recorder of Manchester, said the facts of the case were “frankly chilling”. “You, Mark Buckley, had entered the park intending, as I find, upon attacking and sexually assaulting a female,” he said.

“You were carrying a bag later seen to contain items for sexual activity, together with a length of rope and cord. You were carrying a knife.”

In a statement after her death, Higginbottom’s family recalled her “beauty, love and kindness” and said she had “astonishingly reinvigorated her love of learning over the last few months after some difficult times”.