UPDATE: A federal judge has declared a mistrial in the corruption case of Sen. Robert Menendez.

NEWARK, N.J. — For the second time this week, the federal jury in U.S. Sen. Robert Mendendez's federal bribery and corruption trial has reported that it is deadlocked — a development that suggested the case could soon be headed toward a mistrial.

Just before noon Thursday, the panel sent a note to U.S. District Judge William H. Walls, indicating that it remained at an impasse and that individual jurors were not "willing to move away from our strong convictions" after more than 30 hours of deliberations.

Speaking from the bench, Walls said that asking the jurors to determine whether they could reach a verdict on at least one of the 12 counts the senator faces seemed like a "futile exercise" that could lead down a "slippery slope of coercion."

He began calling jurors back to his chambers one-by-one to interview them in the presence of attorneys on both sides of the case.

Menendez's lawyer, Abbe Lowell, asked the judge for a mistrial.

"It's not that they're just saying they cannot reach a unanimous decision, they're going beyond that and saying they've reviewed all the evidence slowly and thoroughly in great detail…nor are we willing to move away from our strong convictions," Lowell said. "I think we have a for-real hung jury."

Prosecutor Peter Koski, deputy chief of the Justice Department's Public Integrity Section, told the judge there would be "no harm" in asking the jury if it could reach a partial verdict.

"This jury is under the impression it needs unanimity on each count," Koski said.

In the seven days since jurors were handed the case, they have worked mostly in silence — one interrupted when a member of the panel, after being excused by Walls last week due to a scheduled vacation, sketched a vivid portrait for reporters of the jury room dynamic.

Describing a tense scene, that juror, Evelyn Arroyo-Maultsby, said that she doubted the panel could come to a unanimous agreement on any of the bribery counts Mendendez faces. However, she said, the panel was close to convicting the senator on falsifying information about gifts he received from a wealthy benefactor on his financial disclosure form — a felony that carries up to five years in prison.

When the jury returned Monday to resume working, Walls had replaced Arroyo-Maultsby with an alternate and instructed them to start over in their debate. Less than six hours later, they sent their first report of a deadlock.

Since then, the group had remained cloistered without emerging to ask any questions until Thursday's second report of an impasse.

Menendez, a New Jersey Democrat, has denied charges that he accepted a series of gifts including flights on private jets, luxury hotel stays, and large campaign donations from Florida eye doctor, Salomon Melgen. In exchange, prosecutors say, the senator brought his influence to bear on issues important to his benefactor.

Jurors heard nine weeks of testimony and arguments. The trial is in its 11th week.

This is a developing story.