Accelerant has been discovered at the crowded multifamily Queens home where an inferno broke out over the weekend, killing three people, law enforcement sources said Monday morning.

The accelerant was detected by an FDNY canine during a search at the home on 48th Avenue near 90th Street, the sources said.

Recovered video captures a man entering the building before the fire, and walking out before the blaze erupted, according to the sources.

As a result, a search warrant was issued, the sources said.

Investigators are awaiting lab tests, according to a source close to the investigation.

“This investigation is still in the early stages and active,” an FDNY spokesman told The Post on Monday.

The discovery differs from information provided by sources Sunday, who said it appeared the blaze stemmed from an electrical issue.

Police have not identified the three people who died in the blaze that broke out around 5:40 a.m. Saturday, but neighbors said two were trapped behind a locked second-floor door.

Eight residents were reported living there at the time, fire officials said.

The three-family building has been cited 26 times for multiple infractions by the city Department of Buildings since 2010 — yet only one of those violations was settled in the past decade, records show.