The cause of the two-alarm fire that destroyed nine businesses in a Federal Way building complex Sunday will likely not be determined for some time.

In a press release issued Wednesday evening, South King Fire & Rescue Fire Marshal and Deputy Chief Gordon Goodsell said SKFR, the Federal Way Police Department and the Bureau of Alcohol, Tobacco and Firearms are working together to determine the cause. The ATF is assisting in processing the fire scene and conducting interviews. The FWPD has provided an interpreter for witness interviews and will be responsible for criminal investigation if one is discovered.

According to the press release, based on fire patterns and early photos and videos, officials believe the fire originated in the north end of the building, 2020 S 320th St., in the Center Plaza across from The Commons mall.

“The volume of fire debris, along with the many potential sources of ignition, makes for a time-consuming and complicated investigation,” Goodsell said in the update. “For this particular fire, the investigation will include bringing in subject-matter experts and electrical engineers to examine the scene. This detailed examination may go on for a couple of weeks.”

Officials set up a fence around the perimeter of the building, and 24-hour security is in place until the investigation is complete.

The fire was reported at 4:25 a.m. Sunday. By the time the first SKFR firefighters arrived at 4:30 a.m., flames were shooting out the front of one of the businesses and through the roof of the 22,000-square-foot building, fire officials reported earlier this week. The complex did not have a fire alarm or sprinkler system.