A 12-year-old autistic boy was hit by a subway train in Manhattan on Tuesday afternoon after slipping away from his caretaker, law enforcement sources said.

The boy was struck by a southbound No. 1 train at the Dyckman Street station in Inwood soon after he ran off at about 5 p.m., the sources said.

He somehow ended up on the subway track bed before he was hit by the train, authorities added. He suffered a severe leg injury and may need to have a foot amputated, a police source said.

Police were investigating how he ended up on the roadbed.

The boy was rushed to Columbia-Presbyterian Hospital.