Brightr Bay of Plenty regional manager Carl Vujnovich said three team members were on-site when the fire started but had been accounted for.
A St John spokeswoman said three people were treated for moderate injuries and were taken to Tauranga Hospital.
Vujnovich said the rest of the Brightr team were off-site in Tauranga homes advising and installing heat pumps, ventilation and insulation.
The cause of the fire was unknown.
"We're awaiting the report from Fire and Emergency New Zealand's investigation," Vujnovich said.
"The wider Brightr team around the country are pitching in to assist us in getting back up and running as soon as possible."
Birch Ave Tyres is two doors down from the building and staff member Rory Kelleher said the flames were higher than the building beside it at one point.
He said he hadn't heard anything prior to the incident.
A Fire and Emergency NZ spokeswoman said the back half of a building that housed an air conditioning company was fully involved with fire when crews arrived.
A police spokeswoman said police were notified of a building fire on Birch Ave just before midday and helped with traffic management.
A Bay of Plenty Times reporter said the corrugated roof at the back end of the building had collapsed and there were large holes burnt through other parts of the roof.
A man standing near the site said he saw the smoke from Baypark and came over.
"It's not every day you see smoke that dark," he said.
The fire prompted a warning from the Asthma and Respiratory Foundation for people with a respiratory condition to stay inside until the smoke cleared.
It said smoke from fires can worsen existing respiratory conditions and cause burning eyes, sore throats and coughing. It could be a trigger for asthma, bronchitis or COPD.