What started last week's Rohnert Park apartment building fire remained unclear Tuesday, reported a city fire official.

Rohnert Park Lt. John Marty said the Beverly Apartments fire still was considered suspicious and that all obvious causes had been ruled out.

The Jan. 21, middle-of-the-night blaze destroyed six apartments where 15 people had lived, burned six cars and damaged two others.

The fire apparently started in the complex carport, which was underneath the old apartments.

Rohnert Park fire officials sought help for the investigation from the federal Bureau of Alcohol, Tobacco and Firearms and a local agent responded.

Marty said some possible evidence was sent to an ATF lab for analyzing.

One possibility was arson and investigators were looking for signs of fuel being used to help start the fire.

While fire officials await lab results, which weren't due for weeks, investigators were talking again to witnesses, reviewing video and finishing their reports, Marty said.

The fire caused about $1 million in damage.

During the fire, some people had become trapped by the flames. A neighbor caught two young children dropped from the second floor and helped others escape with a ladder.

Read more of the PD’s fire and rebuild coverage here