The U.S. judge asked the jury in the first federal lawsuit against Merck & Co's (MRK ) Vioxx to keep deliberating on Saturday after the panel said it could not reach a verdict on whether the drug contributed to the death of a Florida man.

U.S. District Judge Eldon Fallon instructed the nine-member jury to continue talks to try to reach a unanimous verdict in the case, and said he would allow "a reasonable time" for those discussions to continue.

In August, Merck was found liable for the death of a Texas man in state court. A second trial in New Jersey state court exonerated the company in the death of another man.

The jury began deliberations on Thursday afternoon in the case brought by the widow of Richard "Dicky" Irvin, Jr., claiming that her husband died of a heart attack in 2001 because he took Vioxx for back pain.

Irvin, a manager at a seafood distribution business, took Vioxx for less than a month before he suffered the fatal heart attack.

Merck faces more than 7,000 lawsuits claiming the Whitehouse Station, New Jersey-company hid for years the risks of heart attack and stroke linked to its blockbuster drug.

Analysts have said the company's legal costs to fight the cases could total several billion dollars.

Merck pulled Vioxx off the market in September 2004 after an internal study showed use of the drug for 18 months increased patients' risk of heart attack and stroke. Plaintiffs' lawyers have cited other studies that indicated the risks began far sooner.

On Thursday, the New England Journal of Medicine said Merck withheld information about the cardiac side effects of Vioxx when it presented the journal data from a key trial on the medicine's safety in 2000.

Read the NEJM's editorial (pdf)

Merck said it disclosed the events to U.S. regulators in 2000 and publicly in 2001, including in several press releases.

In the federal court case, Merck's lawyers argued that Irvin had an existing circulatory problems and died after plaque in his arteries broke loose and caused a blockage that triggered his heart attack.

The withdrawal of the drug, which was ultimately taken by more than 20 million people and generated more than $2.5 billion in sales for Merck in 2004, contributed to a $25 billion decline in the company's market capitalization.

The Texas widow who won the first case against the company in state court in August was awarded $253 million in compensatory and punitive damages, although that amount is likely to be trimmed to about $26 million because of Texas limitations on damage awards.