The miscommunication of a radio code word, set by NSW Police to signal missing bushwalker Lily Hooper had been found, is being blamed for an officer mistakenly telling the 18-year-old’s distraught family she had survived after eight days missing in the state’s Southern Highlands.

Hooper’s body was on Thursday night retrieved from dense bush in the Nattai National Park, about 120 kilometres south-west of Sydney, where she had been missing since August 12. Hooper was last seen leaving her Oakdale home in Sydney’s south-west that morning, after telling family she was going hiking.

A multi-agency investigation has been launched to examine a series of failures that left Hooper’s parents, Jim and Kirrily Hooper, believing for almost 20 minutes that their daughter had been found alive, and celebrating with loved ones and media gathered at the search base on the edge of the national park.

A police officer relayed the apparent good news to the Hooper family after an SES search party found the 18-year-old around 11.30am on Thursday. About 20 minutes later they were informed the teenager was dead.

Facing questions about the bungle on Friday, NSW State Emergency Service Commissioner Mike Wassing said NSW Police, which was leading the multi-agency search for Hooper, had set the code word and briefed search parties on it. Neither agency has confirmed the code word, citing the ongoing investigation.

The miscommunication may have been sparked by a radio code believed to be used by SES searchers to report that a body has been found, in which they refer to full, half or empty water bottles to signal whether a person is alive, in the event family members may be monitoring the radio. A half bottle of water is believed to indicate a person’s condition is unclear.

“It’s quite common that during search-and-rescue operations, police will set a code for the search-and-rescue operators to use with respect to if they find the missing person,” Wassing said.

“In this case, there was a code that was applied. We’re working currently with police with respect to any of the misinformation associated with that code or any subsequent further information or communication.”

Wassing said investigators were focused on identifying how the miscommunication occurred and preventing a repeat, rather than blaming a particular agency or its officers. Whether the SES crew that found Hooper relayed incorrect information to the search base would form part of the agency’s investigation, he said.

Authorities say the relaying of the correct information to Hooper’s family was probably delayed by poor radio signal, which is also being investigated as potentially contributing to the initial miscommunication.

The use of radio codes during missing-persons searches was being reviewed as part of the SES’ investigation into Thursday’s events, Wassing said.

NSW Police Commissioner Mal Lanyon was forced to apologise for the miscommunication.

Facing a second day of scrutiny, Lanyon said the miscommunication was not born of ill will but elation that Hooper had been found. Police sought to correct the information at the earliest opportunity.

“Tragically, her condition was miscommunicated, and for that I apologise,” he said.

Emergency Services Minister Jihad Dib said the state government would work with the SES and NSW Police to gather details around the search-and-rescue operation broadly, and the miscommunication.

“This is not about an issue of looking [at] who’s to blame, this is about an issue of working out what it was that happened,” he said.

NSW Premier Chris Minns was forced to apologise to a budget estimates committee after incorrectly announcing that Hooper had been found alive.

“The government, myself, we’re profoundly sorry,” Minns said on Friday.

Minns said he hoped to speak with the Hooper family personally in the coming days.

The information was passed from police to the premier via Police Minister Yasmin Catley. Lanyon said this was not unusual for a high-profile investigation.

Almost 1000 searchers from the Australian Defence Force, NSW SES and the Rural Fire Service had scoured dense bush in the national park alongside police looking for Hooper since she was reported missing. Hooper’s Hyundai was found near the start of the Bonnum Pic walking trail, a challenging 16-kilometre hike, shortly after she was reported missing.

Wollondilly Performing Arts Centre and Wollondilly Shire Library were lit up in purple on Thursday evening to commemorate Hooper’s death.

Wollondilly Shire Mayor Matt Gould, whose electorate encompasses Nattai National Park, said flags on the council chambers would be flown at half-mast.

“They are small gestures but I hope they help show in some way just how deeply Lily’s loss is being felt across our community, and how much Wollondilly is thinking of her family, friends and everyone who loved her,” he wrote on social media.

Bujutsu Martial Arts and Fitness Centre, where Hooper had trained in Muay Thai and Brazilian ju-jitsu for the past two years, also paid tribute. She was months away from receiving her blue belt in Brazilian ju-jitsu.

“She was a talented and tough martial artist, but despite that toughness, Lily was such a lovely person. She was one of those people who everyone simply liked,” Sensei Mark Szalajko wrote on social media.

“She earned the respect, trust and friendship of everyone who had the privilege of training alongside her.”

A post-mortem examination is expected to be held in the coming days to determine Hooper’s cause of death, while a coronial inquiry to explore the circumstances around her death will also investigate the miscommunication.