A funeral director was devastated to find their family-run business torched overnight in a suspicious fire.

Police confirmed they are investigating a suspicious blaze at a commercial property in Mt Wellington, Auckland late last night.

Funeral director and co-owner of Aroha Funerals Janet Mikkelsen said she can't comprehend who would target the premises.

"We got a call at half past midnight that there was a fire at the funeral home. We got here and fire engines were here trying to get it out."

Mikkelsen said she believed the fire was definitely "arson".

Fire has damaged the office of Aroha Funerals in Mt Wellington. Photo / Supplied

Aroha Funerals premises in Mt Wellington before the fire. Photo / Supplied

"It's awful and upsetting just looking at our beautiful little cottage," Mikkelsen told the Herald.

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"We are a very little family-run business. There were a lot of meaningful things inside.

"I can't imagine who would do something like this. Families we work with like what we do.

"It's a tapu place, why would someone do this to it."

The blackened interior of the Aroha Funerals home. Photo / Supplied

Bodies lying inside the building were fine and had been transported to Aroha Funeral Homes' other sites in Meadowbank and Takanini, Mikkelsen said.

Police are treating the circumstances surrounding the fire as suspicious.

"They took off our security system, alarms and switched off the main power," Mikkelsen said.

A message on the Facebook page for Aroha Funerals said: "We are devastated to tell you someone broke into our cottage last night and set two large fires.

"We will not be working out of there for a while, so will be doing office work from Meadowbank and have viewings at Takanini."

Staff said they were "very sad" but would keep going in a bid to provide services to the community.

A police scene guard is in place this morning.