BURLINGTON, WI (WTAQ) - It’s been five days since the Echo Lake Foods plant in Burlington started burning – and firefighters were still responding to flare-ups during the weekend.

Fire Chief Ed Umnus said there are still places underneath the rubble that firefighters cannot get to.

One of the flare-ups occurred Saturday evening, when a pile of rubble started burning.

The state Fire Marshal’s office is helping local investigators try to determine what started the massive blaze – and officials say it could take weeks or months to identify a cause.

Investigators have reported being hampered by ice generated from the all the water thrown onto the blaze.