By Mike Dunn

PHILADELPHIA (CBS) — The union that represents Philadelphia firefighters has filed an unfair labor practice charge against Mayor Nutter over documents related to the Kensington warehouse blaze last April that claimed the lives of two firefighters.

Firefighters Local 22 filed the complaint with the Pennsylvania Labor Relations Board, asking the board to force the Nutter administration to turn over internal documents about the Kensington fire.

Union chief Bill Gault says he requested the documents back in July and has not gotten even a reply.

“We requested the regular audio of the job (recordings of radio communications) and any written reports filed by the officers.  We want to do our own investigation, because clearly the city’s not doing theirs,” Gault said today.

The fire on April 9th (top photo) turned tragic when Lt. Robert Neary and firefighter Daniel Sweeney went to check out a neighboring building and a wall collapsed on them (see related story).

Now, Gault says, answers need to be found.

“We lost two of our best and bravest there.  And we want the truth to be known so it never happens again,” he says.

The union earlier called for the resignation of Philadelphia fire commissioner Lloyd Ayers and two top deputies for how department leaders handled the blaze (see related story).

A spokesman for Mayor Nutter says the administration cannot comment on pending litigation.