A mistrial was declared yesterday in a federal bid-rigging case against five Tidewater contractors and two paving firms when the jury said it was unable to reach a verdict after 9 1/2 hours of deliberations.

U.S. District Judge J. Calvitt Clarke Jr. of Richmond dismissed the jury at 11:30 a.m. yesterday, after the jurors, in their second day of deliberations in the two-week trial wrote a note to Clarke that "We have a divided vote on each defendant. Some of us feel there is a reasonable doubt as to the guilt of all defendants.We regretfully submit we can make no further headway."

The trial was the first in Virginia to result from an 18-month federal probe described as one of the widest ranging criminal antitrust investigations by the Justice Department in history. The five officials and two of their corporations, federal prosecutors charged, had conspired illegally for 16 years to determine which of them should be low bidder on local, state and federal road paving contracts and to submit phony bids to guarantee the agreements in four Tidewater cities.

When the mistrial was announced, according to observers, the defendants their families and their lawyers showed little emotion.

"We certainly appreciate the long consideration the jury gave to the case," said Wayne Lustig, attorney for defendant Wilbert B. Siviter, a former vice president of Rea Construction Company. "We're just going to have to see where the government goes from here."

Lustig said the prosecutors and defense attorneys would meet with Judge Calvitt Tuesday Morning to establish a new trial date, but it was unclear yesterday whether the government will undertake a new trial.

Though prosecutor Hays Gorey said top U.S. Justice Department officials would make the final decision on a new trial, he said yesterday he would recommend further prosecution.

Lustig speculated, in a telephone interview yesterday, that the government "having put forth their best case and apparently not having prevailed," may not decide to go forward with their case.

However, assistant prosecutor Diane Kilborne seemed positive about the possibility of a new trial. "We know where the weakeness in our case are now."

The defendants in the case included Clinton M. Teets and Ralph H. Breakfield of Contractor's Paving Company; R. Curtis Saunders Jr of Portsmouth Paving Corp.; Leighton S. Gaddy of Ames and Webb, Inc.; and Siviter.

Before this trial, Ames and Webb and its president pleaded no contest to the charges, and Rea and two of its officers pleaded guilty to similar charges, as have two other Tidewater asphalt paving firms, Ashland-Warren, Inc. and Asphalt Roads Materials Co. Inc.

The prosecution had alleged those six firms met regularly to divide road surfacing projects among themselves. The government relied mainly on the testimony of paving firms officials who pleaded guilty to build its case.

As early as Friday, in their first day of deliberations, the jurors had indicated they were having problems reaching a verdict. In a note written to Judge Clark, not released until after the trial ended, the jurors said: "It appears we have reached an impasse. Some of us feel the government has failed to prove beyond a reasonable doubt any guilt, while others feel guilt has been proven by both testimony and evidence . . . Is there anything you can say that might help break this impasse?"