Family members of 7-year-old Andrew Rankins Bell, a Philadelphia boy who was abducted from his elementary school three days ago by his bipolar mother, are still in a desperate search to find him.

The mother, Malekah Rankins Bell, lost custody of the boy to his aunt and uncle in March, which police say is a possible motive behind the abduction, according to FOX affiliate WTXF.

Click here to watch the report by FOX affiliate WTXF

The FBI is now aiding the search because local officials don't think the mother and son are still in the Philadelphia area. Malekah Rankins Bell has not used her cell phone since Tuesday morning when she abducted her son and does not have credit or bank debit cards for police to track, WTXF reported. Her family is concerned for the welfare of both of them because of the mother’s mental health issues.

"We just want to let you know, Malekah, if you're watching, that we love you. You are my baby sister you know that we love you, and not only are we concerned for Andrew we're concerned for you," Felicia Morrison, Malekah Rankins Bell's sister, said in an emotional appeal, reported WTXF.

"I thought it would be over by now and it's starting to take a toll," added the boy's uncle, Keith Morrison. "God is our source and we're trusting and believing in God that he will bring Andrew home. But I'm fearful because Malekah is not thinking clearly."

Police and detectives are now posting flyers at busy intersections to help locate the boy. They have been working on the case 24 hours a day.

"Anytime you have ... on many occasions they turn up on a 24-hour period. We're into the fourth day and it's starting to get concerning," said Philadelphia Police Sgt. Charles Layton.

Malekah Rankins Bell was last known to be living in Los Angeles and the boy's uncle, Keith Morrison, did not know she was in Philadelphia, police said, reported The Philadelphia Inquirer.

The Bluford Elementary School from which the boy was taken is now under scrutiny. School officials who let Malekah Rankins Bell take the boy from school were not aware of the court order barring her from contact with him because of abuse, the newspaper reported.

Click here to read The Philadelphia Inquirer story

WTXF also reports that the school district of which Bluford is a part of has surveillance tape of Malekah Rankins Bell entering the school building and later leaving with the boy without being stopped. The district has not yet released the video.

Philadelphia Schools CEO Paul Vallas said Rankins Bell took the boy after recess, telling a local NBC affiliate, "Obviously, you know, somebody should have been watching."

He added: "The mother then followed the children back into the building and took custody of the child once the child was back in the building, according to the other kids, the kids who were standing in line at the water fountain."

Vallas admitted the teacher should have questioned Andrew's disappearance.

"The bottom line is you're supposed to count your kids. You're supposed to make sure that you have the same number of kids in your class after recess as you had before recess," Vallas told the station.

Click here to read the local NBC story