TULSA, Oklahoma - An elderly woman was seriously injured in a house fire and investigators are suspicious about how it started.

The fire department responded to the call at about 5 a.m. Friday morning, in the 100 block of North Yorktown. But investigators spent the entire day there looking for evidence.

They deployed a team that typically handles arson fires and meth labs routinely, though they've not said anything about what might have happened there.

Fire was pouring out the front of the house when firefighters arrived. With other houses very close, and word of a woman inside, they focused on the rescue and protecting surrounding houses.

"They had to go defensive almost immediately, because the structure was unsound and the roof was caving in," said Tulsa Fire Chief Stan May.

Firefighters pulled an elderly woman out a side window. She was taken to the hospital in serious condition. Three dogs were inside and one of them was killed. Before firefighters arrived, several neighbors tried to help.

"Me and my son-in-law kicked in the door, I got a few feet in the house, but it was full of smoke and fire. We couldn't breath and we both came out," said the neighbor Ed Swanson.

Another neighbor Troy Taylor said, "It was shooting 20 to 30 feet above the roof of the house, it was that intense. I was glad she survived, because to tell you the truth, I didn't think really she made it, I really didn't."

The fire marshal and Tulsa Police both responded with investigators to look for the cause.

"[There was] quite a bit of damage, and a lot of debris when the roof caved in and they're going to dig thru that," May said.

The neighbors have varying opinions about what may have happened to start the fire, but all seemed to have kind words for the victim, who they all described as "grandma."

"[She is a] nice old lady, never had a bad thing to say about anybody, so my heart goes out to her," Taylor said.

As of Friday evening, the woman was listed in fair condition at a Tulsa hospital.

The police department is involved in the investigation along with the fire department, but neither department has reported what they've found.