A fatal accident that happened last fall at the same Texas (search) refinery rocked by a deadly explosion this past week was caused in part by inadequate safety procedures and lack of training, according to an internal report.

The company that runs the refinery is adopting reforms to prevent a reoccurrence of the September accident in which two workers were fatally burned by a spray of 500-degree water and steam, BP (search) spokeswoman Marti Gazzier said Saturday.

BP PLC produced the confidential report into the September accident during a court hearing Wednesday, the same day the nation's deadliest petrochemical accident since 1990 killed 15 people and injured more than 100 others at the Texas City (search) refinery.

Officials said it could take months to find the cause of the explosion at the 1,200-acre plant near Houston. About 70 workers and 30 residents of the area were injured, and five people remained in critical condition Saturday.

According to BP's analysis of the Sept. 2 accident, three pipefitters were repairing a water pump when a seal broke loose as one of the men drove a wedge between two flanges. The seal failure caused the release of high-pressure water, immediately followed by superheated water and steam from a boiler, scalding the workers. One of the men survived.

The report said the men assumed a "check valve" was closed. The company cited the pipefitters' decision-making and judgment, but also said its policies and training did not specifically address the potential hazard about valves.