PHILADELPHIA (CBS) – Officials are talking about the environmental impact of the explosion at the Philadelphia Energy Solutions Refinery in South Philadelphia in June. The hearing was held at the University of Pennsylvania and started at 11 a.m.

The owners of Philadelphia Energy Solutions were invited to the hearing but chose not to come.

A huge fireball lit up the sky in South Philly after the explosion erupted inside one of the refinery’s butane tanks around 4 a.m. on June 21.

Major Explosion, Fire At Oil Refinery In South Philadelphia

Four people were hurt in the incident.

It also resulted in Philadelphia Energy Solutions announcing it would close the facility.

More than a month since the incident, fire investigators still have not released what caused the explosion.

A lawmaker asked the State Department of Environmental Protection about that information.

“There were no regulated, DEP regulated facilities in the area of the explosion so we haven’t been involved in that part of the investigation,” said Josh Adams, of the Pennsylvania Department of Environmental Protection.

The hearing is also focusing on the environmental impacts of the refinery and that some guidelines are not being followed.