Southland flooding: Road between Invercargill and Dunedin re-opens

Southland is no longer isolated as the access route between Invercargill and Dunedin re-opens. 

Several roads in Mataura, however, remain closed, Emergency Management Southland says. 

Motorists in the area have been urged to proceed anywhere with caution and only travel if it's necessary.

Civil Defence says further road assessments will be made on Thursday morning.

"It is anticipated that these key assessments will begin at 8am," Emergency Management Southland said on Facebook.

"It is important people do not go around cordons or come into contact with floodwaters.

"Please stay put and stay safe."

Meanwhile, fears a toxic ammonia gas may be released in Mataura from an old paper mill will also be assessed by Fire and Emergency New Zealand (FENZ) on Thursday.

The mill is in the flood zone and houses ouvea - a substance that, when mixed with water, creates the toxic gas.

"We hope to provide residents with an update on the FENZ assessment [at] approximately 10am," Emergency Management Southland says.

"Once we have this information, it will help to inform us of time estimates for residents to be able to return home."

Airbnb hosts are also being urged to open their homes to displaced people. Spokesperson Susan Wheeldon says they are grateful to those who have already offered their homes. 

Airbnb is encouraging anyone living near affected areas to consider doing the same.