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Detective Senior Sergeant Damon Wells said this morning all options in the search for Warrington had been "exhausted".
Warrington was last seen on Main South Rd, Rolleston, at 7.30pm on Saturday.
"Despite incredible support from our search teams and the public, we have exhausted all viable search area options at this time," Wells said.
"We have continued to have regular contact with Shirley's family and have advised them of this.
"They understand that we won't hesitate to initiate further physical searches as new information comes to hand."
Warrington and her husband were stopped by police as part of a routine traffic operation at BP Rolleston on Saturday night.
"They have then travelled, we believe, to Ferrymead, possibly Ferrymead Historic Park," Wells said yesterday.
"He's sat in the car, her husband, while she's gone on a bit of a walk and essentially hasn't returned."
Her disappearance is not thought to be suspicious.
An extensive search for Warrington has been completed, which included the area on and around Ferry Rd, Bridle Path track and Tunnel Rd.
Wells said Warrington's husband is not very well.
"It's been quite traumatic for him. His recollection has helped us locate an area she could be," Wells said.
"He's really concerned about her, as are her family as well."
CCTV footage showed the couple's car entering the Ferrymead area with two people in it at about 8.30pm on Saturday.
At 10.20pm, the car has left via the Bridle Path track and Ferry Rd and 10 minutes later an image was captured of the car with just one person in it.
"We believe he's been driving around trying to find her and had no luck. Somewhere in that two hour time frame their vehicle was in the Ferrymead area."
Wells said the situation had been amplified by the cold weather.
Yesterday he said police were "massively concerned" as Warrington had been missing over three "really, really cold nights" and she was "certainly not dressed for the weather".
Temperatures reached -1.6 deg C in Christchurch on Monday night and -4.5 deg C on Sunday night.
Warrington is believed to be wearing the same black dress she is wearing in the picture released by police.
If you have information that could help the case, phone 111 and quote file number 210711/8724.
-Additional reporting NZ Herald