A large air tanker has been brought in from New South Wales for waterbombing, the first time it has been used across the border, while dozens of fire crews and six other aircraft continue to fight the flames.

Fire and Emergency Services Minister Craig Crawford has signed a disaster declaration for the Gladstone local government region, including the areas of Baffle Creek Catchment, Wartburg, Deepwater, Agnes Water, Round Hill, Miriam Vale and Bororen.

"These areas are under threat of fire or have already been hit by fire and the disaster declaration will ensure that the necessary agencies, including fire and emergency services and police have the powers they need to respond effectively," he said.

"This includes giving police the power to forcibly remove residents and to stop them returning to their homes until it is completely safe."

The Queensland Fire and Emergency Services said residents in Deepwater, Baffle Creek, Rules Beach and Oyster Creek should evacuate on Monday afternoon, as one of the large bushfires closed in.

The fire was expected to reach those communities by 4.30pm and any locals that had already evacuated were being urged to not return because conditions were too dangerous.

Affected locals should flee west towards Miriam Vale using Tableland Road and Fingerboard Road and head towards the evacuation centre at Miriam Vale Community Centre, 41 Blomfield Street.

The second fire continued to burn north-easterly in Deepwater National Park and was expected to hit Bousgas Drive in Round Hill and Anderson Way in Agnes Water on Monday afternoon.

Residents were being told to prepare to leave by QFES and if they did want to flee, they should head north on Bousgas Drive and Anderson Way.

Firefighters were working to contain both fires, but could not guarantee every home would be protected. Power, water, and mobile phone reception could also be lost.

Hundreds of homes remain at risk and two have already been destroyed, but reinforcements were streaming across the border as 100 NSW rural firefighters headed towards the flames on Monday.

Ms Palaszczuk said much of the state was in the grips of "unprecedented" heatwave conditions.

Flames 10-12 metres high have been reported by fire crews on the front lines, with the bushfire having already covered 11,000 hectares and forced the closure of Wartburg State School.

QFES commissioner Katarina Carroll said more property could be have been lost, with fire crews searching through scorched areas to see if any caravans, boats or vehicles have been destroyed.

As many as 500 properties were under threat on Sunday and similar numbers remained at-risk on Monday, according to Ms Carroll.

Bureau of Meteorology senior forecaster Dave Grant said heatwave records stretching back 20-30 years had been broken as a series of dry westerly winds sweep across the state.

The fires, about 115 kilometres north of Bundaberg, continued to burn overnight and fire crews were still trying to contain the flames, which have forced 300 people to flee.

Queensland Fire and Emergency Services said the bushfire started in Round Hill on Thursday afternoon and by the time it reached Deepwater National Park on Saturday, it had split into two separate fires.

Gladstone MP Glenn Butcher said he had met with Agnes Water mayor Matt Burnett and about 300 people had been evacuated so far. QFES said there were 600-800 residents in the evacuation area.

QFES Inspector Andrew Sturgess said Monday marked the fourth consecutive day of extreme fire danger in central Queensland.

"The very dry winds and extreme heat have seen extreme fire behaviour ... and pushed the fire into the Deepwater community," he said.

"Under some conditions, we can’t suppress the fire and at the peak of the day, all we can do is ensure people are our fire crews are safe and use defensive strategies.

Winds were expected to be 25-30 kilometres per hour on Monday, an improvement on the 40 kilometres per hour gusts on Sunday.