Mycogen Seeds, a unit of Dow AgroSciences LLC, and Pioneer Hi-Bred International agreed to pay a combined $18,700 to settle charges they failed to adequately protect their experimental crops in Hawai'i from contaminating other crops growing nearby. Neither company admitted or denied wrongdoing.

Neither company was accused of actually contaminating unmodifed crops. But Pioneer Hi-Bred must perform tests on unmodified corn growing in adjacent fields to ensure none of those crops was contaminated.

An increasing number of consumers are concerned about the health consequences of genetically engineered food, even though not a single sickness has been reported.

The government and biotech industry are under pressure by food processors and biotech foes to toughen rules for growing pharmaceutical and industrial crops. The Grocery Manufacturers of America, for example, wants biotech companies to stop using corn and soybeans ­ which are widely used for food ­ as vehicles for growing biotech products that humans and animals are not supposed to eat.

"There are so many unknown impacts of genetically modified organisms," said Doreen Stravlinsky, a Greenpeace scientific adviser.

Last week, another biotechnology company, Prodigene Inc., agreed to pay the U.S. Department of Agriculture more than $3 million in penalties for mixing genetically engineered corn containing an animal vaccine with soybeans meant for humans.

Pioneer and Mycogen are experimenting with corn engineered with a bacterium's genetic material. The corn is designed to be resistant to the rootworm pest and the genetic modification allows the corn to produce its own pesticide, reducing reliance on traditional chemical sprays.

Neither company's corn modified for rootworm has been approved for human consumption. Each had to agree to rigorous pollen containment. The alleged violations on the islands of Moloka'i and Kaua'i were uncovered by EPA inspectors in March.

The EPA said Dow's Mycogen did not properly surround the experimental corn with trees and unmodified corn to serve as a "windblock" to inhibit pollen spread. Dow said Thursday the alleged violations were the results of administrative errors and that the food supply was never threatened. The company agreed to pay $8,800 in penalties.

"We are disappointed with our performance in this instance," said Dow vice president Pete Siggelko. "We're convinced that what we did provided for improved protection of the environment. But it wasn't consistent with what we said we were going to do. That's a significant administrative oversight, and we're taking steps to ensure that it does not happen again."

The EPA accused Pioneer of planting its genetically modified corn too close to other crops and at an unapproved location at its Waimea Research Center on Kaua'i. The company agreed to pay a $9,900 fine.

A Pioneer spokesman didn't immediately return a telephone call.