The fire happened about 30 minutes after midnight at the facility that was once known as the Montgomery County North Incinerator. The incinerator has been shut down for a decade or so.

Fire officials said the facility is now being used as a waste transfer site. There is also a lot of recovery work conducted, workers pulling recyclable materials from the trash.

Firefighters found huge piles of debris burning in a large semi-enclosed concrete area when they pulled up.

There were no visible sign of flames but there was an incredible amount of choking smoke, swirling in clouds that often moved in so thick that firefighters couldn't see their own trucks parked just twenty feet away.

Firefighters first attacked the fire using hand-held lines to spray water and then added water guns mounted on the tops of truck decks.

Some firefighters also pulled out thermal imaging devices in order to see the hottest spots in the piles of debris.

They said they had their most success when they had workers from Montgomery County come in and use front-end loaders to help pull push and pull debris apart and separate it into smaller piles of trash that could be drenched with water and extinguished.

Firefighters said they are not sure if they will ever know what sparked the flames. Butler Township Fire Marshal Mike Blakesly said, "With this type of fire, it's hard to say, it could be a chemical reaction, it could be spontaneous combustion, it could be batteries igniting, it'll probably be left to the imagination exactly what started it."

Investigators said they finally managed to bring the fire under control around 4 a.m.

Firefighters said there should be no health concerns either from the billowing overnight smoke or the water run-off from the fire.

They also said damage will be almost non-existent. The huge piles of debris are stored in a facility that has concrete walls and floors, the smoky fire created no permanent problems.