Working with the police, firefighters had evacuated the immediate area and businesses, as well as the waterfront. Trains moving through the area had been stopped.
Brown said they were working with a favourable wind but expected this area of the CBD to remain cordoned off for at least another one or two hours.
A Bay of Plenty Times reporter at the scene said cars are crawling along Devonport Rd in both directions, are being turned around at the roundabout at the beginning of The Strand, and are having to head back on Devonport Rd.
"One commuter just vented his frustration at the police officer at the cordon, saying the cars should be turned back earlier, at the traffic lights on Devonport Rd," he said.
The Strand is home to many of the city's restaurants and bars.
A man who works nearby and was evacuated said he could smell the gas in the office.
A fireman came in and told them to evacuate, he said.