When they were young, Patricia and Joan Miller sang and danced for Bing Crosby, troops and their friends.

But as the identical twins grew older, they became less interested in socializing. When people called, the sisters came up with excuses to get off the phone. Without explanation, they stopped sending birthday cards to a childhood friend. And on the rare occasion when they left their home, the two women didn't chat up the neighbors.

Never married and without children or pets, the Miller sisters withdrew into their four-bedroom home in California's South Lake Tahoe, where they were found dead last week at the age of 73. One was in a downstairs bedroom and the other was in the hallway just outside.

It was as if the two sisters, long each other's only companion, could not live without each other, said Detective Matt Harwood with the El Dorado County sheriff's office.

"My perception is one died and the other couldn't handle it," said Harwood, who has been unable to identify any close friends or family members to inform of the sisters' deaths. "It appears purely natural, but we are still trying to piece it all together."

Police don't usually release the names of the dead without first informing their relatives, but the sisters' shrouded lives made that impossible, Harwood said.

"The circumstance surrounding their death is somewhat of an enigma," he said. "These two only ever had each other, and we would like, at least for their sake, to notify their family."

The deaths have confused some residents in the resort town of South Lake Tahoe, where homeowners tend to be close-knit and the sisters' reclusiveness had long inspired questions and concern. Police and neighbors alike are struggling to understand why or how two beautiful women with show business experience shut themselves up in the same home for nearly 40 years and then seemingly died within hours of each other.

In the past year, there were hints that something was amiss at the Miller home. A neighbor spotted an ambulance at the house a year ago and assumed they had fallen ill. Someone asked police to check regularly on the house. When someone arrived Feb. 25 for a routine check, no one answered the door. The next day, police forced their way in and found the bodies.

There was no blood, no signs of struggle. Nothing indicated that the women had persistent health troubles. Their longtime home was not disheveled or unkempt, potential signs of mental or physical illness. Autopsy reports were pending.

Harwood said he called a nearby senior center to see if the sisters were visitors, but no one there had heard of them. He checked with Meals on Wheels volunteers, but it didn't seem that the sisters had received their services. The only relative he found in his preliminary searches was the sisters' deceased mother.

As news of the deaths spread, former South Lake Tahoe residents called police to report that they had lived near the sisters for decades in some cases, and had hardly seen them. One sent in a postcard that claimed the sisters were the only remaining members of their family after their mother's death and their brother died at war.

Calls Tuesday to several longtime residents and social groups in the area turned up little, as many community leaders said they had never heard of the sisters.

Joan Miller was a senior accounting clerk in the payroll department at the Lake Tahoe Unified School District from 1979 to 1984. Patricia Miller, who drove a white convertible with red upholstery, worked in the El Dorado County's social services office during that same time.

"I never heard of anyone else being in either of their lives," said Betty Mitchell, 89, who supervised Patricia Miller in the social services office and saw the twins around town. "They were inseparable and really identical."

The sisters were friendly and often told stories of their singing adventures. They told Mitchell they had performed at Yosemite National Park and when their mother came to visit from Oregon, they all dined at Mitchell's home.

But the sisters were also guarded. When Mitchell urged them to join a community choir, they declined. They never discussed their social lives.

"They kept things to themselves," Mitchell said. "I don't even know if they had siblings."

The sisters grew up in Portland, Ore., before moving to the San Francisco area, where Joan Miller attended college, Harwood learned. The women briefly appeared on a 1950s television show called the "The Hoffman Hayride" and posed for a picture with Crosby as children. The twins also entertained troops at military bases, a childhood friend told Harwood.

The sisters never seemed interested in dating or expanding their social spheres. They listed each other as their next of kin, Harwood said.

"All they had was each other and that's actually the way they wanted it," he said.

Joyce Peterson of the International Twins Association, a social group based in Oklahoma, said she once heard of 100-year-old twins who died within days of each other.

"As a twin, you've got this bond, you're close — almost like a married couple," said Peterson, of Minnesota, who serves as co-vice president of the group with her identical sister. "It's a bond no one else can understand."

The Miller twins appeared in poor health recently and possibly had been treated a year ago for dehydration or malnutrition, Harwood said.

Their childhood friend told Harwood that the sisters stopped sending annual birthday cards last year, and when the friend called to inquire about the missing card, the sisters seem disinterested in continuing the relationship.

Neighbors would call and the sisters would say, "Let me call you right back," and then wouldn't.

"They weren't taking care of themselves as they should or could have," Harwood said.