PORTLAND, Maine (AP)   About a million gallons of partially treated sewage spilled out of a Maine wastewater treatment plant and into a bay, taking a section of a popular trail with it.

The overflow happened on Thursday morning in Portland and closed East End Beach while washing away a section of Eastern Prom Trail. The Portland Press Herald reports the wastewater overflowed from a treatment tank and poured into Casco Bay.

A spokeswoman for the Portland Water District says the cause of the spill was still under investigation on Friday. The spokeswoman says it was the first time the plant had experienced an overflow of this kind.

The popular trail damaged by the overflow is closed, and barricades have been placed around the sections that are unsafe.