A natural gas explosion that killed a 12-year-old girl and injured four others in Dallas earlier this year wasn’t the only one that rocked that neighborhood, according to the National Transportation Safety Board (NTSB), which is investigating the incidents.

The Feb. 23 blast was preceded by two other natural gas events in that area, on Feb. 21 and 22. The NTSB says multiple leaks were identified by Atmos, the natural gas service provider, during its assessment of the Durango Drive incidents and that numerous other leaks in the vicinity have been identified since.

Those discoveries prompted the evacuation of more than 300 residences.

The NTSB has inspected the accident site; pressure tested pipe; collected records of the pipeline operations, pipeline integrity management program and emergency response and conducted interviews of Atmos and the Dallas Fire-Rescue Department personnel.

It has issued a preliminary report on the investigation but has not yet determined a cause.