Houston ? Jurors considering whether Merck & Co.’s Vioxx contributed to a man’s death told the judge Saturday they could not reach a unanimous verdict, but the judge told them to keep deliberating.

The nine-member federal jury so far has deliberated more than 12 hours in three days.

“It is your duty to agree on a verdict if you can do so without surrendering your own conscientious opinion,” U.S. District Judge Eldon Fallon told jurors.

The judge told the panel that if they fail to reach a unanimous verdict, the case would be tried again, resulting in additional cost, time and effort by both sides. He added that another jury wouldn’t be any more qualified to consider the evidence.

The panel is considering whether the drug was defective, if the company failed to warn about its risks and was negligent in designing and marketing Vioxx.

If jurors answer yes, they then must decide whether any of those factors contributed to the 2001 fatal heart attack of Richard “Dicky” Irvin, 53, of St. Augustine, Fla., whose widow is suing Merck.

If the jury finds Merck liable, the punitive damages will be determined in a later hearing.