Federal agents took down an alleged fentanyl pill mill in the Bronx Thursday – the third time in less than a month that authorities busted stash houses containing deadly drugs in the borough, sources said.

At least four people were arrested after multiple agencies raided the two-story home on Beaumont Avenue in the Belmont section of the Bronx Thursday afternoon, according to law enforcement sources.

A pill press, fentanyl, and other drugs have been recovered so far by authorities, sources said.

Neighbors told ABC 7 they heard smoke bombs explode before federal agents entered the house. They were all wearing hazmat suits and face masks, the station reported.

This is at least the third drug bust involving fentanyl to take place in the borough since mid-September.

Investigators discovered a drug mill inside part of a day care last month after a 1-year-old child died from inhaling fentanyl in the Kingsbridge neighborhood, police said. Four suspects are facing federal charges tied to the alleged drug operation.

Then last week more than 40 pounds of fentanyl – valued at $1.5 million – were seized from a suspected drug mill running out of an apartment six blocks from the Bronx daycare where tot Nicholas Feliz Dominici died.

A day care is nearby the house that was raided Thursday, but there was no direct connection, sources said.

The Drug Enforcement Agency, Homeland Security, the NYPD and state police were all on scene Thursday.