OAKLAND, Calif. — Fire officials said Friday they are unable to determine the cause of a fire last month that destroyed an Oakland apartment building that was under construction.

The Bureau of Alcohol, Tobacco, Firearms and Explosives agent Jill Snyder didn’t say what stymied investigators looking into the July 7 fire. The building’s owner, Wood Partners, said it hoped ATF would continue to investigate and ultimately determine a cause.

Wood Partners spokesman Sam Singer said the owners plan to rebuild.

ATF spokeswoman Alexandria Corneiro did not immediately return a phone call seeking comment Friday.

ATF previously determined three similar fires that destroyed two similar construction projects nearby were purposely set.

Investigators released video footage of a “person of interest” seen scurrying up scaffold attached to the side of an Emeryville development shortly before it caught fire in May. It was the second time that $35 million project has been destroyed by arson.

No arrests have been made.

No one has been injured in any of the fires, all of which started in the wee hours.

The July fire prompted the evacuation of 700 neighbors after a construction crane spun out of control for hours.

Oakland Mayor Libby Schaaf said last month that the loss of the planned 196 apartment units exacerbated the region’s affordable housing crisis.