ALVORD, Iowa (AP) — Officials in the northwestern corner of Iowa say about 40 head of cattle have died after eating from a feed wagon that contained a ground-up battery. Sioux City television station KTIV reports the Lyon County Sheriff’s department is investigating the incident at the Alvord, Iowa farm.

Farmer Joel Moser says around 100 head of cattle have been affected by the tainted feed. He says as of Friday night, about 40 had died. He plans to bury the cattle starting this weekend. A toxicology report from Iowa State University showed extremely high levels of lead poisoning.

Sheriff Stewart Vander Stoep says only one farm has been affected by the incident. Investigators are trying to determine whether the incident was accidental or foul play.