SEFFNER, Fla. -

Authorities said on Friday that the house, where the 36-year-old Florida man vanished into a sinkhole that opened up under his bedroom on Thursday night, is "extremely unstable" and is still too unsafe for authorities to extricate the man.

"At this point in time I've been told by our onsite experts that this site is extremely unstable this is not your typical sinkhole..." said Mike Merrill County Administration for Hillsborough County at a news conference. "They've not been able to find boundaries of the underground chasm."

The family of 36-year-old Jeff Bush says there's little hope that he survived what they described as a "black hole."

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Jeff Bush was asleep in his bed when he plummeted into the hole. Right after the ground started to give way under the Seffner home on Faithway Drive, his brother, Jeremy, frantically tried to keep Jeff from sinking into the hole.

Jeremy Bush said he heard screaming coming from his brother's bedroom and when he opened the door, all he saw was a piece of a mattress.  Jeremy Bush said his brother's bed and dresser were missing and described the opening as a black hole.

"I jumped in the hole, tried digging him out and I couldn't get him.  I heard screaming, hollering, but I could do nothing," Jeremy Bush said. "I just want my brother, that's all I want."

The first deputy at the scene pulled Jeremy Bush from the edge of the growing sinkhole, said Jessica Damico, a spokeswoman for the Hillsborough County Fire Rescue.

"When I turned into the bedroom the only thing I saw was a hole and the hole took the entire bedroom," said Deputy Douglas Duval, the first-responder of HCSO, who said he saw the room sinking as he went in and rescued Jeremy Bush. "I looked and I saw no one else in the hole and we turned and we left."

Duval is still trying to wrap his head around the scene he walked into at the house on Faithway Drive.

"I've never seen anything like it. I've never seen anything move so fast and do so much devastation," said Duval. “When I turned into the bedroom, the only thing that i saw was the hole, the hole took the entire room."

Duval managed to help Jeremy Bush out of the massive sink hole, but couldn't save his brother Jeff.

"I got Mr. Bush by his hand and pulled him out I looked and so no one inside the hole," said Duval.

Authorities released the 911 calls Friday afternoon placed moments after the sinkhole opened.

"Um, yes, we need an ambulance... stuck underneath the house," the caller told dispatchers. "The house just fell through."

"The bedroom floor just collapsed and my brother-in-law is in there and he's underneath the house," the caller told dispatchers.

"The mattress, the bed, everything was going down in the hole where the first person had gone," a law enforcement officer said.  "Now, the second person is in the hole trying to save (his brother).  They're not being successful, so (the deputy) just reacted and did what he had to do to get that person out."

Officials have termed the situation a recovery -- not a rescue -- effort. Authorities said there were no signs of life in the house.

"I did everything in the world for him, helped him in every way I could," Jeremy Bush said.  "He was a good guy ... a hard-worker.  I'm just sorry to see that he's gone."

The hole is under the home, which is still standing.  Officials originally said the sinkhole was 100 feet wide and 50 feet deep, but an engineer later clarified the size, saying it's 30 feet wide and 20 feet deep.  He added that soil with a 100-foot "safe zone" was disturbed, and his company is working to determine the boundaries of the hole.

Engineers have been using ground penetrating radar and other tools trying to determine how unstable the yard may be. They ever lowered a robotic camera into the sewer system looking for any cracks in the pipes that may indicate the sinkhole's size.

"Given the size of the hole, I can't not tell you why it hasn't collapsed yet. We don't have an explanation for that," said Bill Bracken, an engineer working with the Hillsborough Sheriff's Office.

"We know the side slopes of the hole is still very steep and the soil is extremely soft based on the soundings we've done on the front and the back of the house," said one engineer, surprised the house is still standing. "Eventually the sinkhole will begin to grow."

The house has been deemed unsafe for rescuers.

"We're going to do everything we can for Mr. Bush,"  said Fire Chief Ron Rogers. "But we need to make sure we don't endanger other people or personnel in the process. Until we know where it's safe to bring the equipment, we are handicapped and paralyzed and can't do a whole lot more than sit and wait."