By CBS3 Staff

PHILADELPHIA (CBS) — Eyewitness News has learned that the Fire Marshal’s Office has finished gathering evidence at the scene of last week’s deadly duplex fire in Philadelphia’s Fairmount section. They have now turned the building over to the Department of Licenses and Inspections. 

The duplex on North 23rd Street is owned by the Philadelphia Housing Authority.

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There were no sprinklers in the units, which are not required under federal law.

Two former fire chiefs are fighting to change that.

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“They were built before the codes and standards required fire sprinklers in them,” Shane Ray, the President of the National Fire Sprinkler Association, said. “But our push is to retrofit these buildings because they’re high-risk occupancies, meaning they have multiple families living in them.”

Twelve people, including nine children, died in the fire.

Investigators have not released an official cause of the blaze, although early reports suggest a child playing with a lighter may have set a Christmas tree on fire.

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If you want to help the victims of the Fairmount fire, click here.