By Elaine Porterfield

SEATTLE (Reuters) - Authorities have found a bunker in mountains near Seattle that they believe belongs to a missing survivalist suspected of murdering his wife and daughter and setting fire to the family home in northwest Washington state, police said on Friday.

Police have been searching for Peter Keller, 41, since Sunday when firefighters responded to a blaze at the family home in North Bend, Washington, and found the bodies of his wife of 21 years and 18-year-old daughter.

"Bunker found at Rattlesnake Ridge of suspect Keller. More to follow," King's County Sheriff's spokeswoman Cindi West said in a tweet posted at mid-afternoon.

Rattlesnake Ridge is in the mountains close to North Bend, a foothill community located about 30 miles east of Seattle.

West could not immediately be reached to provide further details but local media reported that authorities had surrounded the bunker on the belief that Keller was inside. A Reuters witness said law enforcement helicopters were circling over the area.

Peter Keller was known to stockpile supplies and was believed to have set up a "fort" in the woods where he hiked, authorities said.

"Peter was described by friends and family as a loner and had a survivalist mentality," authorities said in court papers.

Authorities added that Keller took over $6,000 out of his bank account before the deaths of his wife, Lynnettee, and daughter, Kaylene, and was said to be preparing for the "end of the world."

One of Keller's co-workers said he owned body armor, and the man gave police a list of firearms that he knew the suspect owned, including several handguns and high-powered rifles with scopes and silencers, according to the court papers.

"He also said that Peter had kept the purchase of the silencers secret from (his wife) because of how expensive they were to purchase," the documents said.

Prosecutors have asked a judge to hold Keller, who has been charged with first degree murder and arson, without bail if he is arrested.

His car was found abandoned at a local library, with the keys in the ignition.

(Reporting by Elaine Porterfield; Writing by Dan Whitcomb; Editing by Alex Dobuzinskis and Jackie Frank)