More oversight and coordination is needed among federal agencies to prevent unapproved releases of genetically modified crops into the environment and food and feed supply, the investigative arm of the US Congress has said.

Since 2000, there have been six known unauthorized releases of GMO crops into the food supply involving GMO corn and rice.

Earlier this week, Monsanto, the leading developer of biotech crops, said some unapproved GMO cotton was harvested. The resulting cottonseed meal may have entered the livestock feed supply.

The Government Accountability Office said in a report  on Friday that more incidents of unauthorized releases could have occurred in the United States and simply gone unnoticed.

The US Department of Agriculture, U.S. Food and Drug Administration and U.S. Environmental Protection Agency regulate GMO crops.

'As pointed out by GAO, the three regulatory agencies still do not adequately coordinate their regulation of the food safety or environmental consequences of these crops,' the Center for Science in the Public Interest, a nonprofit health advocacy group, said.

Each agency contends that the unapproved GMO crops that were released have not caused any harmful effects to people, animals or the environment.

But, the releases have led to food recalls and lost trade opportunities that economists estimate cost producers millions of dollars, the GAO said.

'When unapproved genetically engineered crops are detected in the food and feed supply, food safety concerns rise, markets are disrupted and consumer confidence falls,' said Democratic Sen. Tom Harkin of Iowa in a statement.

Republican Sen. Saxby Chambliss of Georgia agreed that unapproved GMO crops in the market is a problem requiring swift action.

'We must do all we can do to enhance the effectiveness of oversight functions so the technology continues to be available as new products are introduced,' he said in a statement.

Crop developers are subject to periodic inspections, but the GAO says the Agriculture Department lacks the resources to inspect every site and the EPA has not made inspections a priority. Most of the known unauthorized releases were self-reported by the crop developers, the report said.

To boost oversight, the GAO recommended that the FDA make the results of its early food safety evaluations of GMO crops public. The FDA agreed and said it intends to post the results on its Web site.

Also, the GAO recommends that the FDA and Agriculture Department improve their coordination. The GAO suggested developing a formal agreement to share information on GMO crops that could have adverse health implications.

The last recommendation involved all three agencies collaborating to monitor GMO crops on the market.-Reuters