(CNN) -- A Florida exterminator and father of four children adopted from Florida's foster care system has told police that a body found in the pest-control truck he was driving is one of them -- his 10-year-old daughter, authorities said Wednesday.

Jorge Barahona, 53, already faces a charge of aggravated child abuse for injuries to the dead girl's twin, Victor, who was also found in the truck, which was parked on the side of I-95 near West Palm Beach, Florida, officials said.

According to a probable-cause affidavit filed by the West Palm Beach Police Department, a roadside assistance ranger with the Florida Department of Transportation stopped to check the red Toyota pickup Monday around 5:30 a.m. and found the 10-year-old boy inside next to an open gas can.

The boy "appeared to be in respiratory distress and (was) trembling" and his clothing "was soaked with an unknown chemical," the affidavit said.

The ranger then found Barahona on the ground beside the truck and called for help.

The boy was hospitalized in intensive care with severe burns to his abdomen, upper thighs and buttocks, the affidavit said. While examining the boy, doctors noted he had sustained previous injuries, including a broken collarbone, a broken arm, scarring to his buttocks and lower abdomen, and ligature marks on both wrists, police said.

After Barahona and his son were taken to a hospital, a worker decontaminating the truck discovered the body of the girl, wrapped in a plastic bag, the document said.

Barahona told police he was distraught over the death of his daughter, and had intended to commit suicide by dousing himself with gasoline and setting himself afire, the affidavit said. Barahona said he didn't go through with his suicide plan because his son was with him, the document added.

"Basically, to paraphrase, he was stating that he placed his daughter in a plastic bag being distraught over her death," West Palm Beach Police Spokesman Chase Scott told reporters. "He drove here from South Florida accompanied by his son, Victor. He then pulled off to the side of the road saying that he poured gas on his self, intending to light himself on fire. His son's head was in his lap and he decided, after giving his son some sleeping pills, that he wasn't going to do that."

Barahona told police that he doused himself with gasoline and inadvertently got some on the boy, Police Capt. Mary Olsen said.

But, she added, the man's story doesn't add up -- there was no gasoline on the boy. Instead, he was covered with another chemical whose composition had yet to be determined. "That's why we're still treating this as a hazmat (hazardous materials case)," she said.

Scott said the chemicals were so potent that staff caring for the boy at the hospital became ill as well, he said.

Victor, who was transferred Wednesday morning to a specialized burn unit at Miami's Jackson Memorial Hospital, has not been able to talk to investigators because he is on a breathing tube, she said.

Olsen said police would decide how to charge Barahona further once the autopsy on his daughter determines her cause of death.

Asked whether Barahona has expressed remorse, she said, "He feels remorse, but we're not getting consistent statements with what we're seeing in our evidence." She added, "It's a complex case."

At a hearing Wednesday in Miami attended by Barahona's wife, Carmen, a judge ordered that the remaining two children in the home be placed in foster care.

Florida's Department of Children and Families had opened a child protection investigation within the past few days to look into a complaint involving the Barahona family, and it wasn't the first such complaint, spokesman Mark Riordan said.

Reporters in the courtroom Wednesday heard tales of abuse, mainly concerning the twins, from state officials and experts. The caller to the child protection hotline in the latest case reported that the twins were routinely locked in a bathroom for long periods of time and had been bound with tape, the court heard. The story was corroborated by interviews with the other two children in the home, officials said in court.

An investigator told the court that she had showed up last Friday night at the family's home but had not seen the children. Instead, she said, she had left the family's house after speaking with Carmen Barahona, planning to return on Monday. Asked why she had not planned to return sooner, she said, "I'm not allowed to do investigations on a weekend."

However, a spokesman for the department, John Harrell, said it is the job of investigators to follow through immediately or refer to someone else in the department to follow through when a matter is urgent.

CNN's Kim Segal, Shawn Nottingham and John Zarrella contributed to this report