The Nikao-based establishment caught fire in the early hours of Saturday morning.
A police officer raised the alarm and the Rescue Fire Service was at the scene shortly after 4.30am to contain the fire.
Two fire trucks attended the incident. The fire was fully extinguished just before 5am.
Cook Islands Police Service detective inspector Areumu Ingaua said his officers were at the scene completing an inspection of the site.
He said police had not ruled out foul play in the incident.
“We started doing the forensic examination of the site on Monday and that is still ongoing. We have closed the area so no one is allowed to come into the site while we do our work,” said Inspector Ingaua.
“We will continue with our forensic investigation until we are satisfied with everything that we need to conclude this investigation.
“At the moment, we are keeping an open mind into this investigation.”
Efforts to get comments from First Windows and Doors yesterday proved futile. The company referred all queries regarding the fire to the police.
This was the second fire within 24 hours on the island. At around midday on Friday a fire on the back road in Aroa destroyed a Bluesky Cook Islands core site, causing major disruptions to mobile, internet and landline services in Rarotonga and Aitutaki.
Services in the outer islands were also affected.