WASHINGTON — The head of the Food and Drug Administration Monday renewed her call for passage of stalled legislation to give her agency more tools to ensure food safety and prevent dangers such as the salmonella outbreak that has sickened at least 2,000 people and led to the recall of 550 million eggs.

As the investigation into the cause of the nearly two-week-old recall continued on Monday, political pressure began building on regulators and the operators of the two egg-laying operations believed responsible for the outbreak, with congressional overseers seeking information about conditions at the egg farms and about the rigor of federal oversight of them.

Two Iowa egg producers with ties to each other, Hillandale Farms of Iowa Inc. and Wright County Egg Farms, voluntarily recalled the eggs in a series of announcements beginning Aug. 13. FDA officials described the product withdrawal as one of the largest egg recalls in history.

An FDA food safety official said that barring further investigative developments, the recalled eggs should not expand beyond the current total.

FDA Commissioner Margaret Hamburg said her agency needs the authority granted in the proposed legislation to order recalls, instead of relying on private businesses to pull back products on their own.

The House passed food safety legislation in July 2009 and a Senate committee approved similar legislation, with bipartisan backing, in November. But the latter version still hasn’t made it to the floor for a vote by the full Senate, partly because of more pressing legislation, such as the health care overhaul, and partly because of concern that some lawmakers would attach amendments that would derail it.

The bill also would require food producers to implement safety plans, give the FDA more access to company records and make it easier to trace the sources of contamination.

Hamburg noted the “unfortunate irony” that new rules specifically governing egg safety went into effect July 9, too late to change the course of the outbreak.

Hamburg said she believed that had those rules been in place sooner, “it would very likely have enabled us to identify the problems on this farm before this kind of outbreak occurred.”