Deloach Reed said she asked the ATF for help because the department only has one investigator on the scene looking into the blaze.
"That one fire investigator, with all the damage to the building, was not going to be able to conduct an effective investigation by himself," Deloach Reed said.
The department has a total of three fire investigators.
Oakland fire officials briefed the ATF team at the scene Wednesday morning.
Investigators have repeatedly said they have no preliminary information on what may have started the fire.
The ATF help comes as Oakland fire investigators continue to look for witnesses who may have seen the beginning stages of the blaze that sent flames shooting into the sky, forced dozens of nearby residents to flee from their homes and pushed smoke into a wide area of the city.
Oakland officials issued a statement Wednesday afternoon, urging the public to contact them if they have information about the blaze.
Investigators have not yet been able to get inside the gutted building.
"The scene is not safe yet," Oakland fire investigator Weldon Clemons said.
Inspectors have red-tagged the building and barred most members of the public from entering it, according to David Harlan, engineering manager for the city's Planning and Building Department.
"City inspectors will make periodic monitoring site visits," Harlan wrote in an email.
City officials asked the structure's owner to help shore up the building to make it safer for investigators to enter it.
Athan Magganas, manager of Adelphos LLC, the property's owner and developer, did not respond to requests for comment.
"It might take a couple of days for them to stabilize the structure," Deloach Reed said, adding that officials were concerned that scaffolding from the construction and the structure's remaining walls could collapse.
The ATF team has experience in helping make large fire sites safer for investigations, Meiman said.
Deloach Reed said the ATF was considering bringing in a crane to pull out some of the debris.
The federal involvement in the probe is the second time in the last five months that the ATF has assisted in looking into a large construction fire in the East Bay.
In early July, a five-story apartment building under construction in Emeryville was destroyed in a six-alarm fire.
The ATF completed its role in that blaze and the Emeryville Police Department has taken over as the lead agency investigating the fire. Police officials say their investigation is ongoing.