A body believed to be the 2-year-old Bronx boy who vanished a month ago was discovered floating in the East River, swaddled in a blanket Wednesday morning, sources said.

Investigators believe they found little Montrell Williams’ lifeless body around 12:20 p.m. near the Whitestone Bridge just off Ferry Point Park in Queens, according to the sources.

He was wrapped in a blanket and wore only a diaper and a single sock, the sources said. 

Montrell was last seen May 10, when he was with his 20-year-old dad, Arius Williams, according to the sources.

The young dad took Montrell to a Mother’s Day gathering, where he apparently got into a scuffle with his own mother and stormed off with the toddler, sources said.

Surveillance footage taken that night allegedly shows Arius throwing a black bag into the Bronx River, sources said.

In the days to come, the boy’s concerned 17-year-old mom called the cops, who appeared to have told her they couldn’t intervene if her son was on a regularly scheduled visit, the sources said.

When both parents ran into each other on the street Sunday, Arius allegedly pulled a knife on his ex and claimed he threw their son off the Bruckner Bridge, according to the sources.

Arius was taken into custody Monday on custodial interference charges, after refusing to tell a family court judge his son’s whereabouts, cops and sources said.

He did not immediately face any other charges Wednesday.