The federal corruption trial of New Jersey Democratic Sen. Bob Menendez ended in a mistrial Thursday after the jury reported it is hopelessly deadlocked.

Judge William Walls declared the mistrial after interviewing several jurors Thursday.

"I find that you are unable to reach a verdict and that further deliberations would be futile and there is no alternative but to declare a mistrial," he said.

The mistrial is a blow to the Justice Department, which has been investigating Menendez for nearly five years, but leaves the senator without the clear vindication he had hoped for in court.

Prosecutors did not immediately announce whether they will refile charges against Menendez, but any delay at this point helps Democrats who want to hold onto his Senate seat and virtually eliminates any realistic possibility that Republican Gov. Chris Christie -- who leaves office on January 16, 2018 -- could select the senator's replacement if he resigned or was removed from the Senate.

The seven-woman, five-man jury initially told Walls it was deadlocked Monday after several hours of deliberations. A note Thursday says jurors have reviewed all the evidence "slowly," in great detail and are not willing to change their positions.

"We have each tried to look at this case from different viewpoints but still feel strongly in our positions, nor are we willing to move away from our strong convictions," the jury wrote, according to Menendez attorney Abbe Lowell.

Menendez faced charges of conspiracy, bribery, and honest services fraud related to abusing the power of his office that could carry decades in prison. Prosecutors say the senator accepted more than $600,000 in political contributions, a luxurious hotel suite at the Park Hyatt in Paris, and free rides on a private jet from a wealthy ophthalmologist, Dr. Salomon Melgen, in exchange for political favors.

Both men deny all charges.

Defense lawyers argue that Menendez and Melgen were longtime friends with no corrupt intent to commit a federal crime, and after over two months of testimony, prosecutors never produced a smoking gun in the form of a document, email or incriminating phone call outlining an illicit agreement between the two men.

Prosecutor Peter Koski argued passionately in favor of an additional jury instruction that would encourage jurors to consider a partial verdict. But Walls said he was concerned about going down the "slippery slope of coercion" at this stage.

11-week trial

The trial -- which stretched on for 11 weeks -- included 57 witnesses and hundreds of exhibits, but the central factual allegations were never in dispute.

"This case really isn't about what happened," Lowell told jurors during opening statements. "It's all about why it happened."

Prosecutors relied mostly on circumstantial evidence to prove their case -- spending the opening weeks of trial painting a jet-setting lifestyle of the rich and powerful before ultimately turning to the "official acts" they argued Menendez did to help his friend.

They accused Menendez of pushing officials to help resolve an $8.9 million Medicare billing dispute in Melgen's favor, while the defense team claimed at trial that the senator was focused on the fact that the billing policies at issue were conflicting and the drug companies were enjoying a windfall.

Similarly, when several State Department witnesses testified that Menendez has threatened to hold a congressional hearing if they did not intervene in a contract dispute between Melgen and the Dominican Republic over cargo screening at the nation's ports, the defense said that the senator was troubled by port security more generally.

Last week, a juror excused for a long-planned vacation to the Bahamas telegraphed the divisions in the jury room and predicted a mistrial.

"It's going to be a hung jury," said Evelyn Arroyo-Maultsby, who told CNN she would have voted to acquit on all charges if she had stayed on the jury. "I know there's a few that feel the same way I do and they're going to hold their own."

This story is breaking and will be updated.