Citing evidence of "modern-day slavery" and abuse in South Florida's tomato fields, a Senate committee pressed growers on Tuesday to raise the pay of migrant workers and improve their living conditions.

Sen. Ted Kennedy of Massachusetts and three fellow Democratic senators called the conditions for migrant workers on South Florida farms "shameful" and an example of how the nation has neglected people who toil for low pay in backbending jobs while trapped in substandard housing.

Consumers would be shocked at the working conditions of people who harvest Florida tomatoes, members of the Senate committee on labor said at a hearing Tuesday.

"Their working conditions are deplorable, but most of them are afraid to demand fair treatment because they know they'll be fired, blacklisted or turned over to immigration officials," said Kennedy, the committee chairman.

A Collier County sheriff's investigator and other witnesses cited instances of tomato pickers being slapped or beaten, locked into tiny trailers, chained to a wooden post, held behind barbed-wire fences and forced to work to pay off debts for food and housing.

"At the rate they are paid, it's hard for them to ever get out of that debt cycle," Detective Charlie Frost said. "If they decide to leave or want more money, then there's the threat of violence."

The Coalition of Immokalee Workers and other critics call such conditions "modern-day slavery."

The senators were disturbed that growers had resisted an offer by McDonald's and other major food chains to pay an extra penny a pound for Florida tomatoes to boost worker pay. The Florida Tomato Growers Exchange, an industry group based in Maitland, threatens to impose $100,000 fines on growers who accept the offer.

Reggie Brown, executive vice president of the exchange, told the committee his group does not oppose attempts to help workers, but it does not want growers to distribute the additional penny per pound. He said participation could lead to charges under a racketeering law because it would be impossible to fairly sort out how much extra pay to give each worker.

Brown said the industry strongly opposes forced labor and has taken "progressive steps" to prevent abuses by labor contractors. He said growers provide competitive wages, which are based on the number of tomatoes picked, that amount to nearly double Florida's minimum wage of $6.79 per hour to the more than 30,000 workers during harvesting season.

Higher wages could leave growers unable to compete against cheap imports from Mexico, he said.

"We believe that ultimately fast-food chains and other companies will buy tomatoes elsewhere, most likely Mexico," Brown told the committee. "If that business shifts offshore, not only will tomato harvesters be without the extra penny, they will be without jobs."

The senators, who said workers cannot possibly pick enough tomatoes in an hour to come close to $12, were not swayed.

"If Florida tomato growers can't live with workers being paid a penny a pound more, then I can live without tomatoes from Florida on my hamburger," said Sen. Richard Durbin, D-Ill. "And I think most Americans would say the same."

Sen. Bernie Sanders, an Independent from Vermont, said he will request an investigation into wages and working conditions in the tomato fields by the Government Accountability Office, the research arm of Congress.

"Some might say, 'This is a local Immokalee issue, it is a Florida issue.' No, it's not," said Sanders, who visited Immokalee in January. "In America today, we have a race to the bottom. What I saw in Immokalee is the bottom. And if we do not lift that bottom up, every worker in America is in danger."

He also indicated the committee would try to broaden labor laws to cover migrant workers.

"We're not letting up," Kennedy said. "We want everybody to know, particularly the growers, that we're staying on this."

William E. Gibson can be reached at wgibson@sun-sentinel.com or 202-824-8256 in Washington.