(CNN) Two more bodies were retrieved Thursday from the ruins of a burned Maryland mansion , where six people are thought to have died. Relatives of the family released the names of the four youngest victims, authorities said.

The bodies were transported to the medical examiner's officer for autopsies and identification, Anne Arundel County Fire Department Capt. Russ Davies said in the statement.

"There are still two occupants unaccounted for," he said. "This remains a complex scene and much work remains to be done."

Technology executive Don Pyle, his wife, Sandra, and four grandchildren are feared dead in the fire. Officials said the two bodies have not been identified.

Relatives identified the grandchildren as Alexis (Lexi) Boone, 8; Kaitlyn (Katie) Boone, 7; Charlotte Boone, 8; and Wesley (Wes) Boone, 6. They are the children of Sandra Pyle's sons, Randy and Clint Boone, according to the statement.

The children were visiting their grandparents for a sleepover because Monday was a school holiday, a family spokeswoman said.

"On behalf of the Boone and Pyle families, we wish to express our gratitude and appreciation for the love and support being shared with us during this tragic event," the family's statement said. "We are blessed that so many family, friends and neighbors have come together for us in our time of need."

The statement confirmed the identities of the six people firefighters and others have been searching for in the ruins of the waterfront home.

"Our love for our family is boundless," the statement said. "Our loss demands time and quiet reflection to process these feelings. We ask that you respect our need for privacy. Life is fragile. Make time today to embrace your loved ones."

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For the first time since the fire broke out, local and federal officials were able to secure the structure and access the foundation of the 16,000-square-foot house on Wednesday. Cadaver dogs led them to the bodies, officials said.

Officials would not discuss where the bodies were or the possible cause of death.

Authorities are treating the house as a crime scene. Officials said it is standard procedure for a case such as this and no evidence has been found to indicate suspicious activity.

The sheer size of the structure and the fact that three-fourths of the building had collapsed into the basement, with deep piles of debris still smoldering, compounded the search, Anne Arundel County Fire Capt. Robert Howarth said Tuesday. He is leading the investigation along with a team from the federal Bureau of Alcohol, Tobacco, Firearms and Explosives.

The sheer size of the mansion has compounded the search for the missing, an official says.

"You're looking at five standard houses put together," he said Tuesday. "This is more of a commercial fire than it is a residential fire. There are a lot of businesses that aren't 16,000 square feet. That adds to it."

Pyle had not been heard from on Monday, and his colleagues at ScienceLogic were "hoping for a miracle," CNN affiliate WJLA-TV in Washington reported.

Heavy equipment was brought in to aid in the search for victims and clues, a process that could take days.

"We have some very unique challenges with this house," Howarth said. "The construction of the house contained a lot of very heavy materials. We're looking at some steel beams that weigh in the area of 7 tons."

When the first firefighters arrived on the scene early Monday, they received conflicting reports about whether the family may have been out of town. But after interviews with relatives, it was determined that six members of the family were missing, fire officials said.

Fire officials said they were alerted to the fire about 3:30 a.m. Monday. About 80 firefighters responded.

The ATF national response team responded because the fire was deemed suspicious, Howarth said.

The fire department said crews had difficulty putting out the fire because the house is secluded, apparently with no fire hydrants on the scene.

Fire crews had difficulty battling the blaze because the house is so secluded.

Photos the fire department posted on Twitter showed hoses stretched for long distances. Davies said it took hours for fire department tanker trucks and a fire boat on an adjacent creek to bring the fire under control.

Pyle's company biography described him as an industry veteran who has held multiple CEO positions, with more than 25 years' experience in information technology infrastructure software and hardware management.

Pyle told The Washington Post last year that after holding positions in a family business, he decided to look for an "industry that was in its infancy and something that would have growth potential." He started in a sales position in a firm that connected computers over transmission lines, and later sold both hardware and software components for the Internet.

Pyle told the newspaper he eventually moved from sales to sales management to general management positions. In 1992, the company went public and was sold to Cisco Systems five years later for $4.2 billion, according to the Post.