State investigators are digging into rumors that some Idaho and eastern Oregon onion growers used an unapproved pesticide on their crops this year, the Associated Press reports. The pesticide carbofuran, sold under the brand name Furadan, is manufactured by FMC Corp. Though it is used on several crops including potatoes, sugar beets and alfalfa, it is not specifically approved for use on onions. It is designed to control thrips, an insect that feeds on some types of produce. The agriculture departments in both Oregon and Idaho, where harvests are under way, are investigating the matter, officials said, talking with chemical retailers in the region and interviewing onion growers. It''s not clear what danger, if any, is posed by using the pesticide on onions, Idaho Department of Agriculture spokesman Wayne Hoffman said. Officials in both states, A worker with the Environmental Protection Agency apparently heard the rumor that some growers were using carbofuran about two weeks ago while attending an onion field day. Idaho growers can face fines of up to $3,000 for each illegal use of the pesticide, he said, and Oregon growers face fines of up to $1,000 per offense.