PITTSBURGH -- Arson investigators from city and federal agencies were back at the Ebenezer Baptist Church on Wylie Avenue in the Hill District Monday.

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Timeline: From The Fire To The Fall Injured Firefighter Describes Blaze

Demolition crews working along side fire investigators are trying to see what caused the fire that claimed the lives of two firefighters and injured more than two dozen others.

At a press conference on Sunday, city officials said that a board of inquiry would be established to look into the actions of the firefighters.

The cause of the fire is not considered to be suspicious and appears to be accidental but further investigation is needed to determine the exact cause, according to Capt. Francis Deleonibus.

A memorial service is scheduled for Thursday at noon at St. Paul's Cathedral in Oakland.

WTAE Video Ebenezer Timeline: From Fire To Fall North Side-Oakland Procession Funeral Mass, Gun Salute, Flyover Funeral Mass - Bishop's Opening Remarks Funeral Mass - Chief's Condolences

Demolition teams worked on Sunday to knock down any loose building material to make the scene safer for investigators.