OCEANSIDE, Calif. — Investigators have ruled out arson as a possible cause of a fire that engulfed the far seaward end of Oceanside Pier last week, causing extensive damage and forcing an indefinite closure of the historic seafront landmark in the northwestern corner of San Diego County.
Analysis of the scene of the blaze, which gutted a vacant restaurant building and a snack shop after erupting shortly after 3 p.m. Thursday, points to an accidental cause of some sort, according to the Oceanside Fire Department.
In conducting such investigations, "we look at what we can rule out and what we can't rule out," OFD Chief David Parsons told reporters Monday afternoon during a briefing near the charred pier.
"And everything leads us to believe, based on canine (searches), reports, videos, witness interviews, fire dynamics, which is how fire moves, and then also patterns that we see in the structure ... that an incendiary liquid, which could be indicative of potential arson -- none of that's present," Parsons said.
WATCH: Drone captures extent of Oceanside Pier damage
Video evidence and witness interviews suggest that the fire started on the northwest side of the pier -- possibly underneath the promenade deck -- next to the former Ruby's Diner site, which was undergoing renovations at the time of the blaze, according to city officials.
"We haven't nailed (it) down to a (precise) point of origin," Parsons told news crews. "Ideally, that's where we want to get, but I don't know if we're going to get there with how much damage is out there. ... So really, by the process of elimination, we're going to the accidental cause, but that doesn't mean we can a hundred percent nail it down, because we don't have the device or the item that may have actually been involved. And that may or may not ever be found."
During an all-out multi-agency effort that continued for more than 24 hours, crews were able to save roughly 95 percent of the iconic 1,950-foot-long wooden structure, according to city officials. Emergency-services personnel from agencies across the county battled the flames from atop the burning pier, aboard a pair of firefighting boats and in water-dropping helicopters as the blaze sent a towering plume of black smoke to the east. The Coast Guard sent in a cutter to aid in handling the emergency.
Over the course of the around-the-clock firefight, crews put a "trench cut" in the deck, removing a section of it to allow for access to flames burning underneath it and to prevent the blaze from traveling any farther down the pier to the east, the fire chief said.
The city has been working with a contactor on installation of temporary fencing to block off the damaged end of the pier, allowing for a partial reopening during repairs, officials said.
Coast Guard-enforced restricted areas around the pier -- 100 yards for vessels and 100 feet for swimmers and surfers -- remained in effect this week.
Exactly when the public will regain access to the tourist-attraction structure remained unclear Monday, though city leaders were committed to reaching that goal "as quickly as possible," Parsons said.
WATCH RELATED: Oceanside Pier fire under control, but still smoldering