Olivia Day provided the update on Facebook and said police were handling the case with high priority after her brother went missing from his Bristol home more than two days ago.
"Thank you to every single person who has spread our message around the world. Now we just need good news," she wrote.
Avon and Somerset police were unable to confirm the update.
Earlier, Day's fiancee Kelsey Mulcahy told the Herald she was frustrated that police initially deemed his disappearance as low risk and would not track his phone.
Mulcahy last heard from him around 9.30pm on Saturday (local time) - he had stopped texting her but she just thought he had gone to bed early. The next morning she called him around 9am and still got no answer - but she thought he was just sleeping in.
Around 2pm that day she arrived back home from London to their flat in the Bristol suburb of Clifton and he wasn't there - their bed was still made, curtains were drawn and all that were missing was his keys, wallet and phone.
Mulcahy told the Sydney Morning Herald that the last text she sent him was to remind him to pull down the blackout blinds. He had replied "will do".
Day, a former TVNZ camera operator from Auckland, has now been missing for more than 48 hours and Mulcahy is terrified that he has been hurt.
Mulcahy faced long interviews with Avon and Somerset police officers and search teams on Monday, and she said search efforts had been slow to kick off.
"The frustrating thing is that his phone is on and they're not tracking it," she said earlier. "They said they don't have permission because he is not a high risk because I described him as not being suicidal or at risk to anyone else and because he is solidly built, he's a male and he can take care of himself at this stage," said Mulcahy.
"I know if we tracked his phone that would take us five steps ahead."
Mulcahy said family back in New Zealand were "panicked" and "distraught". Day's parents and her mum are due to fly over tomorrow to help find him she said.
"It's hard because there are so many people that love him in New Zealand, his family and all of his friends adore him – he's just the sweetest, nicest guy ever," said Mulcahy.
Mulcahy said the couple had various plans in place - they were supposed to travel to Bath today for a getaway, Day had just brought them tickets to see Chris Rock in London and they were flying back to New Zealand at the end of the year to get married.
They had just moved to Bristol after Mulcahy was offered a job with a mental health start-up there, and Day was working as a builder. She said they know no one in the area.
At most, Mulcahy said, Day, who is working as a builder, would have only left their flat to go out and get takeaways for dinner.
"His plan was to have a really nice night in at home, having the flat to himself," she said.
Day is described as 5'11'' tall, with tattoos on both arms and was most likely wearing a cap and long wax black jacket.
Day's friends and family, including Mulcahy, have also taken to media and social media to express their concern and say his disappearance is out of character.
Josh Tasman-Jones, Day's best friend, told TVNZ's Breakfast that the best thing people in New Zealand can do is to keep sharing posts on social media.
"Everyone has done everything they can at this stage and we just want to thank everyone for the outpouring of love and support," he said.
Breakfast host Jenny-May Clarkson said on the show this morning that they were all "shaken" and a number of Day's former TVNZ colleagues including reporters Kimber lee Downs and Andrew Macfarlane have posted on social media, also urging help.
Mulcahy said friends, workmates and family in the UK are all out trying to find Day and were putting flyers up.
"There's a big group of people looking now, I just have to stay home in case he comes back."
Avon and Somerset police have urged anyone with information to come forward.
