DALLAS (AP) _ Eight lab workers have been acquitted of falsifying test results in what federal officials had called the largest case of fraud in environmental testing in U.S. history.

Jurors rejected all 77 federal charges Tuesday against the former employees of Intertek Testing Services' Environmental Laboratories. The workers were accused of misrepresenting results in the cleanup of thousands of hazardous-waste sites and other environmental cases in a moneymaking scheme.

All the employees worked at the company's lab in the Dallas suburb of Richardson, which stopped operating in 1998. Five other employees and the corporation pleaded guilty before trial to falsifying lab reports. As part of its agreement, the corporation will pay a $9 million fine.

Prosecutors said Intertek managers pressured employees to bypass procedures required to produce reliable tests in order to complete lucrative government contracts faster.

From 1994 to 1997, the company handled as many as 250,000 samples from more than 59,000 polluted sites nationwide, grossing more than $35 million. The results were used for making decisions at Superfund sites, Department of Defense facilities and hazardous waste sites, and also for monitoring hazards affecting soil and ground water.

Defense lawyers said no irregularities at the company violated any laws governing cleanup efforts, and said the government had no evidence to back up its claims of fraud and conspiracy. During the six-week trial, defense attorneys called only one witness, who testified on a minor point for about 15 minutes.

``This is a bungled investigation on a gigantic scale,'' said Mick Mickelson, an attorney for one of the defendants. ``This investigation was a disaster for the government.''

Former Intertek chemists and managers cleared Tuesday were Chukwujekwun Anozie, Michelle Georgina Delgado-Brown, Gesheng Dai, Martin Dale Jeffus, Michael Lynn Ludwick, Dale Thomas McQueen, Sheila Ann Petty and William S. Wingert.

``I'm disappointed, but the decision is one for the jury,'' said Assistant U.S. Attorney John Bradford, who led the team of prosecutors.

Environmental Protection Agency officials said jurors may not have fully grasped the technological complexities of their case. They also said expensive government efforts to recheck cleanup sites to ensure they are as clean as past Intertek lab work suggested will continue indefinitely.

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On the Net:

Intertek: http://www.itsglobal.com/

EPA: http://www.epa.gov