Clutching a cigarette in a trembling hand, Amy Robinson wiped away tears Tuesday as she stared into the charred ruins of the mobile home where her two youngest children died the day before. She kept thinking of their smiling faces, the sound of laughter now gone.

"All I can do is cry," Robinson, 27, said. "I'm looking at it, and I can't believe it happened. I wish it was just a dream, but it's not. It's reality."

Fire struck in an instant Monday afternoon and quickly consumed Robinson's aged single-wide on North Charleston's Lakewood Street. Robinson and her 4-year-old daughter escaped without injury, but the girl's infant half-sister and 2-year-old half-brother perished in the blaze.

North Charleston fire investigators are still probing the blaze and have not released the cause, but Robinson blamed the fire on a lamp that her son knocked over while playing.

Robinson said she was in the bathroom when the fire started at 3:43 p.m. Her 3-month-old daughter, Tatyanna Green, was in a swing in Robinson's bedroom while her son, Anthony Lazo, played at the other end of the home with his older sister, Savannah Barton, she said.

Robinson said she heard a loud "whoosh." She stepped out of the bathroom and found black smoke and flames in the house, she said.

Robinson said she tried to reach her children, but the fire was too intense. She made her way outside and screamed for help. "I didn't know what to do," she said, her voice breaking. "I tried and I tried, but I couldn't get to them. I was so scared."

Savannah escaped through the rear door, but Anthony did not follow his sister, Robinson said. Savannah's uncle, Mozack Green, plucked the frightened girl from the porch and carried her to safety. She was coughing, her face covered with soot, he said.

North Charleston firefighters were on the scene within six minutes and battled their way into the home in an attempt to save the children, but it was too late, said Bianca Sancic, the fire department's public information officer. Older mobile homes with poor insulation and combustible paneling can go up in flames in three to five minutes, she said.

Cozack Green, Tatyanna's father, said fire officials told him his baby daughter was found dead in her swing. Anthony's body was found beneath a bed, where he had taken shelter from the fire, he said.

Autopsies determined that both children died from smoke inhalation, Charleston County Deputy Coroner Kelly Myers said.

Green, 37, said he felt like he was having a heart attack when he arrived home from work Monday and learned what had happened. Tatyanna was his first child and he had come to love the other children as his own. "It's just so hard right now," he said.

Green, his brother and Robinson returned to the scorched and gutted home Tuesday morning and surveyed the loss. Mozack Green showed them how he smashed a window with a cinder block and a stick in an attempt to get the children out. At their feet lay strands of singed insulation, a scorched child's cycle and other debris.

Yellow tape still circled the home and police made regular swings through the neighborhood to make sure intruders stayed out. Early Tuesday morning, officers arrested a 41-year-old homeless man they found stripping copper wire from the home's air conditioning unit and collecting aluminum siding for scrap, police said. Wilbur Hooks was charged with petit larceny.

Robinson said she has a place to stay for now, but she lost all of her belongings in the fire. She and Green said they hope someone will establish a fund to help them pay for funeral expenses for the children.

Sancic said the fire illustrates the importance of having smoke detectors in homes and having a family plan in place for escaping should an emergency occur. She urged parents of small children to have smoke detectors in each child's bedroom, along with baby monitors to listen in for signs of trouble.

Robinson said she had a smoke detector in the mobile home but never heard it go off Monday.