10:53 AM EDT, 06/26/2024 (MT Newswires) -- The BP (BP) refinery fire that killed two brothers in 2022 was the "last in a series of cascading events" that began about 24 hours before, according to the US Chemical Safety Board's final report into the incident on Monday.

The naphtha release and fire at the BP-Husky Toledo Refinery in Ohio on Sept. 20, 2022, which led to the death of the two BP employees, started with a "relatively minor process upset" in the previous night's shift, the report said.

"The CSB determined the cause of the incident was operators opening valves and removing a flange on the pressurized Fuel Gas Mix Drum to release a flammable liquid, naphtha, directly to the ground," the report said. "After being released to the ground, the flammable liquid formed a vapor cloud that reached a nearby ignition source resulting in a flash fire."

The CSB concluded that the board operators experienced over 3,700 alarms during the 12 hours preceding the incident that overwhelmed and distracted the board operators, causing delays and errors in responding to critical alarms, according to the report.

The CSB said it is issuing safety recommendations to the current owner of the facility but didn't make any recommendations to BP as the company no longer operates the refinery.

"Wherever we work, safety is embedded in everything we do," BP said in a statement sent to MT Newswires on Wednesday. "In the aftermath of the accident, BP actively cooperated with CSB's investigation, and we take external findings such as this into account as we continually implement learnings and recommendations to improve our process safety performance."

Shares of the company fell 1.1% in recent Wednesday trading.

Price: 35.68, Change: -0.41, Percent Change: -1.12