GASTON CO., N.C. -- Gaston County investigators will return to the scene of a house fire that killed a pregnant mother of two was the result of arson.

They will being searching for evidence Thursday morning. Investigators said an arson dog detected an accelerant at the scene, and the victim’s fiancé of four months said he’s sure Wednesday morning's blaze was no accident.

Flames began shooting from the home on Hidden Meadow Court around 3 a.m. Wednesday. Neighbors frantically called 911.

“There’s a lady’s car here. She’s not answering. There’s no way she’s going to survive this,” one caller told the 911 dispatcher. “We think there is someone inside. Please help us.”

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RAW AUDIO: Neighbor's Frantic 911 Call As Gaston County Home Burns

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Authorities said they believe the woman killed was 31-year-old Lucy Johnson. Her body has not been positively identified.

Neighbors said she was a nurse, and a spokeswoman for Cleveland Regional/Kings Mountain Hospital confirmed Johnson had been a nurse there since 2005.

Johnson, who was four-months pregnant, lived in the home with her 7-year-old daughter and 6-month-old son. Authorities said both children were staying with their fathers at the time of the fire and are safe.

One neighbor said she spoke with Johnson Tuesday.

“Things were going good. She was very excited. She was pregnant and she was telling me she was getting married,” said Teresa Colbard.

Colbard said the woman was very proud of her engagement ring.

Investigators won’t say where Johnson’s body was found or if she appeared to have been alert at the time of the fire. They said the fire was so intense that it took firefighters about 45 minutes to douse it.

Investigators said they will take their time combing through the charred remains of the home as they search for evidence and a cause. They said they could be working at the scene through Thursday.

The fire marshal and agents with the State Bureau of Investigation are at the house, along with the Gaston County Arson Task Force. Gaston County police are looking for persons of interest and examining three orders of protection the victim had taken out against two men, one who she said had threatened to cut her with a knife and another who threatened to burn her house down.

Police said they are in contact with the district attorney’s office but they have not talked in depth about the possibility of charges regarding the unborn baby.