Hens are kept in "deplorable conditions" at a Manheim egg and dairy farm, according to a report issued Thursday by the Humane Society of the United States.

The allegations follow a six-week undercover operation at the Kreider Farms egg factory.

According to the report, an investigation in February and March found severe overcrowding, mummified bird carcasses, thick layers of dead flies on the floor and other unsanitary conditions at a facility at 425 Indian Village Road.

Not so, company CEO and president Ron Kreider said in a prepared statement Thursday.

"The allegations by HSUS are a gross distortion of Kreider Farms, our employees and the way we care for our birds," Kreider said.

"Our birds are clean, active and healthy. We believe HSUS's allegations are unfounded."

Tom Beachler, vice president of operations for Kreider Farms, said the Humane Society "grossly misrepresents" conditions at the facility.

"It's fabricated. That's the method that they use," Beachler said in a telephone interview Thursday afternoon. "We have absolutely nothing to hide because we are doing everything right."

Beachler accused the HSUS of staging the film in order to discredit Kreider Farms and whip up support for new legislation protecting hens.

"So many people have been on our farms, they understand how we operate," he said. "That's the bottom line."

Kreider Farms keeps approximately 7 million egg-laying hens at facilities in Manheim, Mount Joy, Middletown and Lebanon. Pennsylvania is the nation's third-largest egg-producing state, according to the Associated Press, and Kreider Farms is among its largest egg producers.

Among the Humane Society's findings:

Hens were kept in cages with only 54 to 58 square inches of space, which does not give them enough room to spread their wings.

Injured, infected and dead hens, including mummified bird carcasses, were found in cages with live birds laying eggs for human consumption.

There was a thick layer of dead flies on the floors.

Hens' heads, legs and wings were trapped in cage wires and automated feeding machinery.

Ammonia levels were so high that workers often had to wear masks, and barns were so dark that workers needed head lamps and flashlights.

Hens were left without water for several days when a water source malfunctioned, causing many to die.

"Their quality of life is miserable day after day after day," HSUS president Wayne Pacelle said. "This situation is intolerable."

The Humane Society also reported instances of salmonella at the facility.

In a statement to the media, Kreider Farms vice president for sales and marketing Dave Andrews said one building tested positive for salmonella and has been cleaned, but no eggs tested positive for the bacteria.

Andrews also said the Humane Society is misrepresenting conditions at the farm.

"They're taking select footage by going through a facility and finding a dead bird or something that may look unsavory, and they're blowing that up on camera and making this look like a representation of how we treat 5 million birds," he said.

The Humane Society is calling for more support of federal legislation that would improve conditions for hens.

Kreider Farms is one of only a few egg producers in the U.S. that does not support federal legislation to improve conditions for egg-laying hens, according to the report.

Although Kreider Farms is not a member of United Egg Producers, an organization partnering with the Humane Society to promote higher standards for egg-producing facilities, Kreider said "we fully support such legislation. More regulation would actually benefit Kreider Farms; with our state-of-the-art facilities, we would have the least to do to comply."

Kreider, in his statement to the press, said Kreider Farms "is considered one of the most progressive egg companies in the United States."

The Food & Drug Administration picked Kreider Farms to help train its inspectors in 2010, he said, and Kreider Farms was awarded the Family Farm Environmental Excellence Award by the U.S. Poultry & Egg Association.

"We are leading the industry by tearing down old traditional-style egg houses and replacing them with new state-of-the-art facilities," Kreider said. "More than 80 percent of our chickens are housed in larger, modern cages.

"By comparison, 80 percent of U.S. caged egg production still houses birds in older, traditional-style cages."

Kreider also questioned the legitimacy of the Humane Society report.

"We have no evidence of undercover activity inside our facilities, and there is no evidence that HSUS video footage was taken inside Kreider Farms. There are still many unanswered questions regarding how and when this video was shot, edited and assembled," he said.

"Based upon HSUS's recent accusations, three official, spontaneous inspections of our chicken houses were held on April 11. All three inspections provided us with a 'clean bill of health'."

Kreider Farms came under fire earlier this year after an audit by U.S. Immigration and Customs Enforcement, an investigative arm of the Department of Homeland Security, found that about 100 of its employees - one-third of the Kreider Farms work force - had invalid documents, meaning they were ineligible for employment in the United States.