"We've arrested two people in this multiple homicide, a man and a woman. We still don't have a motive as such, but the suspects are known to the victims," Urquhart said at a news conference Wednesday.

Urquhart said a 29-year-old woman and a man in his early 30s are being held for investigation of homicide and that it's unclear if the two are related.

Police said the two came to the crime scene after investigators arrived there Wednesday morning. They were questioned by investigators, then arrested shortly after 4 p.m.

Urquhart said investigators have not determined a motive for the deaths.

The King County Sheriff's Office said the six, all family members, were found dead at a rural property near Carnation on Wednesday morning.

Police said the victims are a man and a woman in their 50s, a man and a woman in their 30s, a 6-year-old girl and a boy about 3 years old. The six are three generations of a family. Urquhart said all six died from homicidal violence, most likely from gunshots on Christmas Eve. No weapons have been found.

The bodies were found at 8 a.m. by a co-worker of one of the victims who worked at a post office. The co-worker went to the home when the usually reliable postal employee failed to show up for work.

King County Sheriff's Detective Bob Conner initially would only say that there were multiple victims, both male and female, and referred to the deaths as homicides but later Wednesday afternoon the sheriff's office told KIRO 7 Eyewitness News reporter Rick Price that six people were confirmed dead.

Sheriff's investigators had ruled out murder-suicide by Wednesday afternoon.

Connor said officers and a sheriff's helicopter searched the area to determine whether there are other victims.

Video from Chopper 7 showed a large older house surrounded by crime scene tape. The house is on an isolated property in the mostly rural area in the 1800 Block of 346th Avenue Northeast. Carnation is about 21 miles east of Seattle.

The home is part of a cluster of residences at the end of a long dirt road. King County sheriff's detectives blocked the road with crime scene tape and towed away a black pickup truck sealed with evidence tape. Detectives are searching nearby properties.

According to public records, the property is owned by Wayne Anderson, 60, and Judy Anderson, 61.

Mark Bennett, who identified himself as a family friend, said Wayne Anderson was a Boeing Co. engineer and Judy Anderson worked for the Post Office in Carnation.

Bennett said he spoke with the couple on Christmas Eve and tried to call them Christmas Day but could not reach them. He told reporters he came to the property Wednesday morning after seeing the home on television news.

"I didn't want to believe what I heard and saw," he said, "so I drove over."

Bennett said the Andersons have three children. One daughter, Michelle, lives on the property in a mobile home, he said.

Bennett said he used to run a coffee shop with another daughter, Mary, who lives in nearby North Bend. A son also lives in the area, he said.

Police said the site of the slayings was complex and they expected to be at the scene for several hours and into Thursday while the investigation continues.

Conner said there was no ongoing threat to the community.