WASHINGTON (AP) — Congressional investigators say the Iowa egg farm at the centre of a massive salmonella outbreak received hundreds of positive results for salmonella in the two years before its eggs sickened more than 1,500 people.

In a letter yesterday to the company's owner, the House Energy and Commerce Committee says that investigators have obtained records showing that Wright County Egg received 426 positive results for salmonella between 2008 and 2010.

The committee says those results include 73 samples that were potentially positive for Salmonella Enteritidis, the strain responsible for the recent outbreak.

The owner of Wright County Egg, Austin "Jack" DeCoster, is scheduled to testify before the committee next week.