FDNY colleagues of fallen Battalion Chief Michael J. Fahy mourned his line-of-duty death with a bunting ceremony at his West Bronx firehouse Wednesday as authorities held a second man who could possibly be connected to the explosion that had claimed the life of the 17-year veteran.

An NYPD official said Wednesday evening that Garibaldi Castillo, 33, of Washington Heights, had been picked up in relation to the explosion and is likely to be charged with felony marijuana possession.

Another man, Julio Salcedo, 34, of Kingsbridge Terrace, had been picked up Tuesday by a federal fugitive task force on an old NYPD bench warrant and was being held in Cliffside, New Jersey, officials said. He has not been charged in relation to the Bronx explosion, officials said.

Salcedo was seen leaving the house before it blew up, officials said. He and Castillo are both believed to be connected to the property, officials said.

Earlier, Mayor Bill de Blasio said there was a “tragic randomness” to Fahy’s death because others just feet from him survived the blast Tuesday in the Kingsbridge section of the Bronx.

The explosion was so powerful that it knocked the roof off the home, where first-responders were investigating the odor of gas but found marijuana plants and fertilizer .

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“We lost a very, very good man,” de Blasio said on WNYC’s “The Brian Lehrer Show,” noting that Fahy, 44, a Yonkers father of three, was a trained lawyer who chose to follow in his father’s footsteps as an FDNY chief.

De Blasio said NYPD and FDNY investigators were still trying to determine the cause of the explosion and track down suspects in the deadly incident.

“It’s not confirmed exactly what it was, but there is strong indication it was a marijuana grow house,” the mayor said.

On Wednesday morning, hundreds of firefighters — most in dress blues — saluted Fahy at a bunting ceremony at the West Bronx’s Battalion 19 where he was stationed. Uniformed NYPD officers also attended.

FDNY Battalion Chief Michael J. Fahy was killed and at least seven others were injured when a home exploded in the Bronx on Tuesday morning, Sept. 27, 2016. Photo Credit: FDNY Battalion Chief Michael J. Fahy was killed and at least seven others were injured when a home exploded in the Bronx on Tuesday morning, Sept. 27, 2016.

Members of the FDNY Emerald Society Pipes and Drums played and black-and-purple memorial bunting was hung above the bays of his firehouse.

Fahy’s wake will be held Thursday and Friday at a Yonkers funeral home and his funeral services will be held Saturday at Annunciation Church in Yonkers, the FDNY said Wednesday.

With Alison Fox, Charles Eckert, Matthew Chayes and Robert E. Kessler