MADISON, Wis. — Wisconsin environmental officials are working to clean up a manure spill spreading toward the bay of Green Bay.

The state Department of Natural Resources announced Tuesday that surface-applied manure from Betley Farms near Pulaski in Oconto County ran off the site late last week and over the weekend into the Little Suamico River.

DNR spokeswoman Sarah Hoye said Wednesday that the manure was applied on July 8 and July 9. Rain late on the night of July 9 and into July 10 drove the manure off the site into an unnamed Little Suamico tributary, she said. The DNR doesn't have an estimate of the exact amount of manure that reached the river, she said.

The department was notified of the spill on Sunday and staff have been working to clean it up since. Runoff at the site has stopped but the spill was still moving toward the bay as of Tuesday evening. The department has already noted water quality problems and a fish kill on the Little Suamico, Hoye said.

It's unclear what penalties, if any, Betley Farms might face, she said. Asked why the department wasn't notified of the spill for several days, Hoye said residents downstream in Pulaski and Chase were the first to report the run-off via the department's spill hotline. The farm wasn't aware of the spill until the DNR contacted them, Hoye said.

No one immediately returned a voicemail left at a number for Betley Farms on Wednesday. A message left on the farms' Facebook page generated a response of "we will reply later" from an unidentified sender.

Betley Farms holds a DNR permit to operate as a factory farm, defined as a livestock or poultry feeding operation with at least 1,000 animal units.