Police are treating the death of a six-year-old girl whose body was found in woodland on the Isle of Bute on Monday as murder, officers have confirmed.

In a press conference late on Tuesday evening, Police Scotland said a postmortem examination had confirmed that the body recovered was that of Alesha MacPhail. They appealed for anyone who was involved in the search operation that was carried out on Monday to come forward.

“Alesha’s family is utterly devastated by what has happened and the news that we have had to give them this evening,” said Det Supt Stuart Houston. “Alesha was a six-year-old girl who had started her summer holidays and came here to spend her holiday with her relatives.”

Facebook Twitter Pinterest Tributes left to Alesha MacPhail on the Isle of Bute. Photograph: Jeff J Mitchell/Getty Images

He confirmed at the press conference on the island that Police Scotland was treating her death as murder. Earlier, the force said additional police officers had been sent to the island to help the investigation, as well as to reassure the community.

Houston said officers were trying to put together a timeline of the girl’s disappearance and wanted to speak to anyone who had been in the area of Ardbeg Road in Rothesay. He said a forensic investigation was held in the area where her body was found, though officers were still investigating the specific circumstances of her death.

The officer said there were numerous lines of inquiry in respect of how the six-year-old left the house where she was staying and the circumstances surrounding her death, though he offered no further details. Asked if police believed claims she had sleepwalked, he repeated only that police were following numerous lines of inquiry.

Tributes were paid to Alesha, who was a pupil at Chapelside Primary School in Airdrie, North Lanarkshire. Flowers, teddies and balloons were left on the pavement outside a house on Ardbeg Road, with messages attached reading “sleep tight little angel” and “good night little angel”.

Part of the beachfront and a shelter opposite the house remained cordoned off with police tape on Tuesday. Four officers in white overalls entered the back garden while another took photographs of the property, which is thought to be made up of three flats.

Anyone with information is asked to call officers at the major investigations teams via 101, quoting incident no 0695 of 2 July 2018.

Alesha was reported missing shortly before 6.30am on Monday and her body was found about two and-a-half hours later by a member of the public after a large-scale search.

Shortly after the discovery of her body, Houston said: “This death of a six-year-old child has shocked the tight-knit community of Rothesay and it is imperative that we find out what has happened.”