Arrests have been made following Wednesday night's incident when two women were allegedly robbed at gun point.
Police say the women were trying to purchase a vehicle that had been advertised on Facebook.
The Armed Offenders Squad and police stormed a Miriam St property in Masterton last night, executing a search warrant to locate the firearm believed to have been used in the theft.
Two men in their 20s were arrested.
Detective Senior Sergeant Barry Bysouth said one of the men had refused to cooperate during the search and was later found hidden in the loft of the house.
The men were currently being held at the Masterton Police Station.
"The search of the address continues this morning and the men will remain in custody while the investigation is ongoing."
The two victims, a local woman and another visiting the region, had been in their parked car on Roberts Rd near the intersection with French St when two men allegedly pointed a firearm at them and robbed them of cash at 8.30pm on Wednesday.
"One of the victims had travelled to the Wairarapa to purchase a car that had been advertised on Facebook," Mr Bysouth said.
"This is a timely reminder to anyone engaged in online transactions to be vigilant when meeting with potential sellers or purchasers."
He said the women were receiving help from Victim Support.
"They were both obviously shaken as a result of the robbery."
Some Miriam St residents had been blocked from entering their homes, Mr Bysouth said.
"We'd like to apologise for the inconvenience to those residents, and thank them for their patience as we worked to resolve this situation."
One nearby resident said she heard police calling to the offenders.
"When we got home at about 7pm they weren't flashing their lights but they were calling on a megaphone saying 'Come out with your hands up please, come through the front door if you're hiding'," she said.
Police are still keen to hear from anyone with information that may assist with the investigation.