A 13-year-old boy and 14-year-old girl have been interviewed by police over a Snapchat video in which they threatened to harm or kill a young toddler.

Darebin police began investigating the incident after the video was shared to social media on Saturday night.

Fears had been raised for the toddler's safety, but police traced the footage to a house in Preston in Melbourne's north and safely located the child.

The footage shows the teenagers - who claimed they were married and the child was theirs - laughing as they hold a plastic bag over the child's head.

"We're not child abusing them, we're just teaching them discipline," says the boy. "They're not dead, but then they can't breathe."