SEATTLE -

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."