Authorities said Tuesday they are continuing to look for six family members — two adults and four children — who are missing after a fire that destroyed a waterfront mansion in Anne Arundel County and that they are still trying to get inside the wreckage of the large-scale home.

The family members were last seen inside the home on Childs Point Road in Annapolis, according to officials with the Anne Arundel Fire Department. No details have been released from officials as to who may have been in the home at the time of the fire, and officials are saying the family members are “unaccounted for.”

Capt. Russ Davies, a spokesman for the Anne Arundel County Fire Department, said they were “not providing the identities of who the unaccounted for are until we locate them and get positive identifications.”

Because of the severity of the damage at the mansion, where seven-foot beams need to be removed and the roof, first and second floors collapsed into the basement, no firefighters or investigators have been inside the home.

Authorities said at a news conference outside the home Tuesday morning that they were considering the incident as a “serious fire” and were engaged in an “active criminal investigation,” although they cautioned that they had no reason to believe that it was a suspicious fire.

“We have no witness who can tell us where this fire started,” said Capt. Robert Howarth, a commander with the Anne Arundel County Fire and Explosives investigation unit. “We can’t determine the origin without an investigation.”

The cause of the fire is under investigation.

Howarth said authorities were gathering evidence from the scene and that if they “discover a crime has been committed,” they wanted to make sure the evidence is “admissible in a court of law.”

He cautioned, “We enter this investigation with no expectations.” Fire officials said it is standard procedure to handle this type of incident as a criminal investigation as they continue to work the scene.

“If it is a criminal act, we will proceed” that way, Howarth said. “If it is accidental, we will proceed as if it is accidental.” Initially, officials had said they did not have reason to believe there was anything suspicious about the case.

The four-alarm fire broke out early Monday morning in the 16,000-square-foot house. Property records indicate that cybersecurity executive Donald Pyle and his wife, Sandra, lived in the home that sits on eight acres and was assessed at more than $6.6 million.

A neighbor said the home was designed to look like a castle. The home sat behind a large gate and had a small castle as a mailbox.

On Tuesday, a national response team from the Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) was joining the search and investigation at the scene because of the size of the home and scope of the damage, officials said.

The large size of the home was proving to be a challenge for firefighters, they said. Fire officials said they were working to bring in heavy equipment to move heavy beams so they could get inside the home.

“This is five standard-sized houses put together,” Howarth said. He said he expects crews will be able to go inside the home Wednesday once the necessary equipment has arrived on the scene.

“No one has been inside yet because the structure is not safe to put anybody in there,” Davies said. “This house is built more like a commercial building than it is an ordinary house.”

Crews spent much of Monday dealing with “flare-ups” from the blaze. On Tuesday, they were also working to pump water out of the basement. Officials said they expect to be removing debris from inside the mansion for several days.

ATF Special Agent David Cheplak, a spokesman for the agency, said Tuesday that the property was a “complete loss” and that six family members are unaccounted for.

On Monday, authorities said they were told that the Pyle family was preparing to go on a trip and might be out of town. But investigators were not able to reach them by cellphone and have spoken with relatives who could not reach them, either.

“It’s a possibility we have to consider,” Davies said, when asked whether the family might have been trapped inside the burning house. “Our intent is to do that search and look for them.”

Donald Pyle is chief operating officer of ScienceLogic, a Reston-based cybersecurity company that monitors networks for government and private clients. He previously helped launch Juniper Networks of Herndon, Va., and was chief executive of Laurel Networks of Pittsburgh and Netcordia of Annapolis.

In an interview with The Washington Post in October, he said he grew up in northern Baltimore County and worked in a family business as a teenager. He switched to information technology after college, he said, because “I was looking for an industry that was in its infancy and something that would have growth potential.”

Spencer S. Hsu and DeNeen L. Brown contributed to this report.