The house that went up in flames when a 4-year-old was left home alone for 15 minutes Friday had no working smoke detectors, a fire official said Saturday.

Adam Gordon, the Monsey fire chief who led dozens of firefighters from six departments in fighting a Friday afternoon blaze at 485 West Central Ave., said the house had no working smoke detectors.

The fire destroyed the home but injured no one. Only a 4-year-old boy, Alexander Lliguichusca, was inside at the time.

Two good Samaritans who happened to be nearby rushed in and led him to safety.

“We found the child by the door sitting by the bed,” said neighbor Saul Friedman, who was heading toward his car on Herrick Avenue when he saw flames and smoke coming from the house, then called 911 and dashed inside at the direction of the dispatcher. “He was shaking. He couldn’t talk.”

The boy’s father, Manuel Lliguichusca, who lived at the house with his wife, three kids and a few other people, said he didn’t know how the fire may have started.

He said he left Alexander home alone for about 15 minutes while he walked to his brother’s house on West Street to pick up a piece of mail sent from his mother in Ecuador.

Lliguichusca said his wife was at work at the time, and the boy didn’t want to come on the errand with him.

Walking back to the house, he heard an ambulance and returned to find his son standing near a fire truck as smoke poured out of the house.

“I don’t know what happened,” Lliguichusca said.

Shortly after the fire broke out, Ramapo Detective Sgt. John Lynch said an initial report indicated the boy might have started the fire while playing with matches, though other police and fire officials wouldn’t confirm that report.