Cops seized $2.5 million worth of heroin from a Bronx apartment, police said.

Officers with the Manhattan North Narcotics Unit broke down the door of the apartment on Creston Avenue in Fordham Heights at 1 p.m. Wednesday and arrested all 12 people inside, sources said.

The 46th Precinct tweeted a picture of the 140,000 glassine bags of heroin, which were wrapped into bundles.

“It’s one of the biggest [heroin] busts we’ve had,” a law-enforcement source said, noting the raid followed a four-month probe.