A gas main on the corner of Eastbourne St west and Nelson St south in Hastings has been damaged by contractors.
Four fire appliances and police attended.
Incident commander Collin Littlewood said a contractor had dug up the gas main.
"We've got open hose lines to dissipate the gas," He said.
He expected to stay at the scene for the next hour.
"We've also got evacuation and house protection in place to protect people in the area."
More to come.