A missing 6-year-old boy from Texas, whose parents fled to India from the US and face felony charges of abandoning and endangering their child, is believed to be dead, a top police official has said.

Noel Rodriguez-Alvarez, who has special needs, was last seen in November shortly after his twin sisters were born in October last year.

Everman Police Chief Craig Spencer said on Thursday that the search for the missing boy is now a death investigation and they are attempting to locate and recover his body.

“We currently have active felony warrants for the arrest of the mother Cindy Rodriguez Singh and Arshdeep Singh for abandoning and endangering a child, which is a second-degree felony," Spencer said at a press conference.

"We want these fugitives arrested and extradited to the United States so that we can seek answers for the disappearance of Noel,” he said.

Noel was one of ten children to Cindy, 37. Three siblings reportedly lived with grandparents, while Noel and the others lived with their mother in squalor in a shed in Everman, a suburb of Fort Worth. Singh, the boy’s Indian-origin stepfather, also lived in the filthy shack.

The search for Noel began after the Texas Department of Family Services asked on March 20 that police in Everman conduct a welfare check, Everman police have said.

On March 22, Noel’s mother, Cindy, her husband and six children got on a plane and travelled to India, Spencer said, adding Noel was not with them, NBC News quoted police as saying.

Authorities have issued warrants for the arrest of Cindy and her husband Singh on felony charges of abandoning and endangering a child.

They are trying for the extradition of the couple from India, where they fled in March, days after police began investigating an anonymous tip that Noel had been missing since November.

“We are working with our federal partners and they are engaged with us. They're on the case working side by side. As we get more information, we will update," the police said.

"We rely on our relationship with international agencies. When they have information to share back with us, they'll obviously communicate that with us, but they're working on it, ” Spencer said in response to a question on status update with the Indian government.

He said the circumstantial evidence, paired with interviews and work that has eliminated all other possibilities, has led police to believe that Noel is dead.

Investigators came to the conclusion that Noel was likely dead after disproving multiple lies regarding his whereabouts told by Cindy.

The lies include that the boy was in Mexico with his biological father or aunt and that he had been sold to a stranger at a local grocery fiesta market parking lot.

“However, thanks to technology interviews, search warrants and the assistance of authorities in Mexico, investigators verified each one of these claims. Throughout the investigation, we learned that Cindy had been known to be abusive and neglectful," Spencer said.

He said investigators learned through interviews that Cindy referred to Noel as “evil, possessed or having a demon in him” and believed he would harm the twins.

“Relatives and witnesses stated that food and water were often withheld from Noel because Cindy did not like changing Noel's dirty diapers. A relative even witnessed Cindy strike Noel in the face with keys because he drank water,” he said.

When Noel was last seen, he was described as “appearing unhealthy and malnourished,” Spencer said.

Authorities previously disclosed Noel was born prematurely and had several physical disabilities and developmental disorders.

They also described his mother as having an “extensive criminal history” and explained she was the subject of a previous investigation by Child Protective Services, the New York Post reported.

The pair are believed to have fled to Singh’s home country of India before the warrants were issued, it said.

The City of Everman plans to hold a candlelight vigil for Noel at 8:30 pm on Monday at the Everman Civic Center.

On November 1 last year, Cindy obtained passport photographs of all the children living with her except for Noel. The next day, she applied for passports for herself and all six of the children except for Noel.

Investigators continue to work tirelessly to comb through all of the electronic data and other information that has been obtained through a multitude of search warrants.

"We have not located any information that would suggest the child has been sold for traffic. We have additionally been able to disprove stories that Noel was given to other family members,” Spencer said.

“Although the course of this investigation has changed our commitments, we will continue to fight for Noel," he asserted.

The following steps in the investigation will be to try to determine possible locations to search for the boy’s remains.

"We are engaging with several experts and highly qualified organisations to assist us in this venture. Some organised searches have already begun and are expected to continue in the coming days," Spencer said.

The couple lived mostly in a converted shed in the backyard of their home on Wisteria Drive.

Noel and some of his siblings mostly stayed in bedrooms in the main house, according to homeowner Charles Parson.

Investigators thoroughly searched the property, including digging under a concrete patio that Cindy paid to have installed. But the search has not led to evidence of Noel’s location, police said.

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