On Thursday night, tens of thousands of people across Tamworth received a text message that police were searching for missing man, Alexander Schlack.

Oxley Superintendent Kylie Endemi said on Friday it was not a hoax, but a new tool in the belt for police to contact the community in high-risk missing person searches.

"I would reassure the community that it absolutely is valid, any text messages that they might receive from that number which is 0444 444 444 does come from the NSW Police Force," she said.

"It is new technology that we are using to try and get the community's help to locate people that are missing where we think that there is risk in terms of their safety.

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"And what it allows us to do is reach up to half-a-million people in a defined area where a missing person was last seen."

Mr Schlack, who is aged 48 and from Narrabri, has been missing from Tamworth for 11 days.

As a result of the geo-alert that was sent, police uncovered evidence on Friday that Mr Schlack was in a retail store in Peel Street about 5.10pm on May 24.

At the time he was wearing black jeans and a bone or mushroom-coloured long-sleeved shirt, and was carrying two brown paper shopping bags.

Earlier that day, he was also seen at 4.20pm on the corner of Peel and Bourke Street. Police have confirmed CCTV captured him walking at that time carrying a brown jacket.

Police have been told he was also at Tamworth hospital until about 3.40pm, but when he failed to contact family, police were alerted.

Superintendent Endemi said detectives were canvassing parts of Tamworth on Friday as part of their investigation, and police were doing "everything in our power" to find him.

"Certainly we do have concerns because it has been a lengthy period of time now that he hasn't contacted his family and it is out of character," she said.

Police are probing whether Mr Schlack might have access to a vehicle, or whether he used any other transport to get around.

"Unfortunately last confirmed sighting of him was some time ago, on Monday 24th May and that was in Tamworth, so we are asking for anyone with information to please help us so we can bring Mr Schlack home safely to his family," Superintendent Endemi said.

What he was doing in Tamworth is part of the investigation, Superintendent Endemi said.

Alexander is described as being of Caucasian appearance, about 180cm tall, thin build, brown/grey hair and unshaven.

The geo-alert, which included a link, was sent across the Tamworth area at about 6pm on Thursday.

"I know there was a great deal of concern from people as to whether it was actually valid, I know there was concern about clicking on that link, that's why it absolutely is important that we get the message out to people that this is absolutely a valid tool for us," Superintendent Endemi said.

Anyone with information on Mr Schlack's whereabouts, or who might have seen him in the past 11 days, is urged to contact Oxley police on 6792 7199 or Crime Stoppers on 1800 333 000.

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