SEATTLE (AP) — A state Utilities and Transportation Commission investigation says Puget Sound Energy failed to properly disconnect and seal a gas pipeline that caused a natural gas explosion in Seattle in March.

The Seattle Times reports the report said a pipeline between two buildings in a neighborhood north of downtown was left active despite being abandoned in 2004.

The blast sent nine firefighters to a hospital and damaged numerous businesses.

The report says people using the space between buildings to store belongings broke the pipe at a threaded connection. Gas escaped and accumulated inside or under a building before it ignited.

Due to the investigation's findings, a complaint has been filed against the utility alleging 17 violations of pipeline-safety regulations. If affirmed by the commission, the utility could face up to $3.2 million in penalties.

A statement from PSE called the fines "disappointing and excessive."

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