A fire has forced the closure of a New South Wales ski resort weeks ahead of the beginning of the snow season.

Firefighters battled to contain the blaze, described by one official as "an absolute tragedy", given the timing, inside a two-level sewage plant at Charlotte Pass Snow Resort last Friday.

The flames were fuelled by diesel and building products that were being stored at the site.

Fire and Rescue New South Wales Inspector Philip Eberle said firefighters from Perisher helped avoid a potential environmental disaster within the fragile ecosystem of Kosciuszko National Park.

He said 375,000 litres of potentially dangerous treated waste water was "saved and maintained".

"Crews fought the fire for a solid two hours and prevented any hazardous materials reaching the environment by using minimal water instead of foam to extinguish it," he said.

"That goes against a lot of different principles and techniques when fighting a diesel fire, but the environmental damage that could've been caused by using foam was far greater than extinguishing the fire traditionally.

In a statement to the ABC, NSW Police said an investigation was ongoing and that no reports of injuries had been made.

The resort is owned by Australian media and entertainment company Blyton Group, which also owns the nearby Selwyn Snow Resort.

That resort was rebuilt after it was destroyed in 2020 by the Black Summer bushfires.

The company also owns the Snowy Mountains Airport Corporation and the bus service linking Charlotte Pass village to Perisher Valley.

Charlotte Pass is the nation's highest and oldest resort and becomes completely snowbound over winter, when the only access is provided by the Blyton Group-owned bus service.

The snow season is set to begin on the June long weekend and this week company representatives met with officers from the Department of Planning to discuss the next steps.

In a statement on its website, resort chairman Kevin James Blyton said wastewater from taps, showers and toilets could not be processed at the site.

He said the resort would be closed until an alternative option was found.

The options include the restoration of service in sections of the plant that have not been not damaged, using a temporary plant, and trucking effluent offsite throughout the season.

"I must caution that all of these potential options present significant challenges and may not be operationally feasible in the unique alpine region Charlotte Pass is located in, as well as the short time-frame before the commencement of the 2024 snow season," Mr Blyton said in the online statement.

"Charlotte Pass will only progress with a solution where it can be confident on ensuring it can minimise any risk to the sensitive alpine environment the resort operates in.

The ABC has contacted the resort for comment about how existing bookings will be managed.

In 2022 the resort was fined $200,000 by the NSW Land and Environment Court for not maintaining the treatment plant properly.

The penalty was imposed after more than 11 million litres of partially treated sewage leaked into nearby Spencers Creek over 78 days in 2019.