Police dogs tracked the two eldest brothers to a nearby wooded trail where they were arrested

Two daughters survived the attack - a 13-year-old who remains hospitalized and a 2-year-old who was unharmed

They found the bodies of two parents, two of their sons and a daughter

Police were called to a house in Oklahoma following a 911 hang-up call

Two teenage brothers have been arrested after allegedly stabbing to death their parents, two brothers and a sister at their home on Wednesday night in what is being described as the 'worst criminal event' in the Oklahoma town's history.

Police went to the address in Broken Arrow, a town southeast of Tulsa, Oklahoma, after receiving an 'open 911 call' - where someone calls the emergency number but does not speak.

When officers arrived, they found five bodies - two parents, two sons and a daughter - as well as a seriously injured 13-year-old girl and an unharmed two-year-old girl.

While police have yet to identify the victims, they say the daughter who was killed was approximately 5-years-old while the two boys were about 7 and 12.

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Bloodshed: Investigators walk around a pool of blood on the front step of a home in Broken Arrow, Oklahoma where five members of the same family were found stabbed to death late Wednesday night

A worker wheels a gurney with a body bag on it, under the green cover, to a coroner's van outside the home on Thursday

A worker from the medical examiner's office, right, looks down at a body behind the tarp, outside the home on Thursday

A worker does paperwork near a gurney with a body bag on it in the door of a coroner's van outside the home on Thursday

Body bags: Police were called to the house after someone dialed 911. When police arrived at the scene, they started dragging bodies out of the house and onto the lawn, afraid the assailants might still be in the home

Arrested: Two teen boys, 16 and 18, were arrested in woodland near the home on suspicion of carry out the grisly murder of their own family members

The dead adults, a couple, reportedly had seven children - four boys and three girls - News on 6 reports.

Broken Arrow police Cpl. Leon Calhoun said Thursday that officers were unable to enter the home when they arrived Wednesday night. But after hearing moans, they forced their way in and found a 13-year-old girl who survived the stabbing attack. They pulled her outside.

He says officers re-entered the home and pulled two more victims to the lawn because it wasn't immediately clear whether they were dead or if the attacker was still inside. The bodies of three other victims also were found inside the home

Sgt Thomas Cooper of the Broken Arrow Police Department described the scene as 'gruesome'.

Grim discovery: The blood on the doorstep was just the start of what police described as a 'gruesome' scene

'The crime scene has taken a pretty heavy toll on officers who have come out here,' he added. 'It hits close to home, especially when the victims are adults and juveniles. Our officers have a lot to take in.'

He also said: 'It appears that the two suspects fled out the door sometime during our arrival.'

A police K9 unit was able to track the young male suspects to some woods behind the well-to-do neighborhood in Broken Arrow.

They were arrested and brought into custody. One of the teenagers was later taken to hospital, but police have not said why.

Heartland: Broken Arrow is 120 miles north-east of Olklahoma City. Police said the murders were 'almost unprecedented'

Abode: According to public records, the family lived in one of the biggest and most expensive homes on the block, which sold for $245,000 in 2007

They have not yet identified the suspects or the victims, but say they all appear to be related and living in the same home.

The 13-year-old girl who was found alive and suffering from stab wounds was reported to be in a serious but stable condition on Thursday, after undergoing surgery. Neighbors say she is expected to make a recovery.

The two-year-old girl is in protective custody. She was allegedly born prematurely and her parents had recently started a non-profit to help other families who have premature children.

Neighbors say the father worked in the computer industry while the mother stayed at home to home school the children, who were allegedly not allowed to play with the other children in the neighborhood.

Neighbor Helen Hoagland, who has lived in the neighborhood for 42 years, said she sometimes saw the mother outside with several children who she said she kept a close watch on.

'Whenever I'd see the children with the mom, they always seemed OK,' she said. 'I saw them outside playing. I'd see the boys out mowing the lawn.'

Coroner's vans also arrived early Thursday afternoon to remove the bodies that were found about 11:30pm Wednesday.

Two bodies that lay covered in the yard were the first to be removed; they were placed in green body bags and placed in the van.

Sgt Cooper told NBC News the incident was 'almost unprecedented' in the city of around 100,000.

The Broken Arrow Police Department and Oklahoma Bureau of Investigations are investigating.

According to public records, the family lived in one of the biggest and most expensive homes on the block, which sold for $245,000 in 2007.

The neighborhood is reportedly filled with mostly retired couples.