A $10,000 reward has been offered in the search for two fugitive parents in an Oklahoma child abuse case.

Hakim Mustafa Moore, 27, and Robin Alexander, 29, are thought to have fled Oklahoma to Missouri, and law enforcement, including the U.S. Marshals Service, are looking for the pair.

The parents, who had a child who died in 2017 and three who were removed from the couple's custody when officials discovered the children were malnourished, failed to appear in court last month in a child neglect case from 2018.

The child's December 2017 death remains under investigation, Altus, Oklahoma, police department said in a statement Wednesday. St. Louis police have said three of the couple's children are in the custody of the state of Oklahoma.

Officials do not know the whereabouts of a fifth child, who St. Louis police said was born in a hotel room and which was never documented by authorities, is unknown.

Altus police said it got involved in the child abuse investigation in September 2018. An Altus police detective told NBC affiliate KFOR of Oklahoma City that police were called about three children who suspected of being abused.

Court documents indicate that when police searched the couple’s home that month, officers found a "very limited amount of food," the station reported.

The documents say the children, who were were 10 months to 4 years old, were "malnourished due to child neglect by means of starvation,” KFOR reported.

Altus police said the children were treated and released and Moore and Alexander were arrested on counts of child abuse by injury and child neglect. They were out on bond when they failed to show for a court appearance last month.

Warrants were then issued for their arrest, and police trying to find them learned they had possibly fled to the St. Louis area, Altus police said.

Detectives believe they fled the Altus area May 1, and that the fifth child was born around May 2, the Oklahoma police department said.

St. Louis police said Wednesday that the marshals service is offering up to $10,000 for information leading to their arrests.

"Help us get them taken into custody and find the child and make sure the health, welfare of the child is in good shape," Altus police Detective Colby Earls told KFOR.

Phone numbers associated with either Moore or Alexander could not immediately be found in online public records Wednesday night.

Altus is a city of around 19,800 about 120 miles southwest of downtown Oklahoma City.