The search is on for the Bronx man who is believed to have tossed a baby boy into the East River over the weekend.

The baby was discovered by a group of tourists near the Brooklyn Bridge on Sunday.

Law enforcement sources say the man being sought is the baby's father, and that he fled to Thailand.

The man and the child's mother were in a custody battle.

Sources say the mom reported the boy missing when he wasn't returned to her on Monday.

She contacted police after seeing news reports about the baby being pulled from the water.

The NYPD is looking at surveillance video, and trying to track the father's moves.