The jurors in the fraud trial of former media baron Conrad Black have been sent back for more deliberations, after they told the judge Tuesday afternoon they were unable to reach a unanimous verdict.

The jurors had sent Judge Amy St. Eve a note saying they discussed all the evidence and could not reach a verdict on one or more counts. They then asked the judge for advice on how to continue.

The jury's note did not stipulate whether the charges pertained to Montreal-born Black or one of his three co-defendants.

St. Eve later instructed the jury to resume deliberations and "make every reasonable effort" to reach a verdict soon.

Rosemary Barton of CBC News said Black appeared quite relaxed when he arrived at the Chicago courthouse, where the trial has taken place, but he did not offer any comments to reporters.

The nine-woman, three-man jury was in its ninth day of deliberations. After 15 weeks of testimony, more than 40 witnesses and about 700 documents, the jurors were handed the case on June 27.

Late Tuesday afternoon, the jury adjourned and told the judge they would begin deliberating again at 9 a.m. CT.

 Black and three former associates are accused of looting Hollinger International of more than $60 million US, mostly through non-compete payments made following the sale of hundreds of Hollinger-owned U.S. and Canadian community newspapers.

Black was charged with nine counts of mail and wire fraud, one count of racketeering, one count of obstruction of justice and two counts of tax fraud. He faces more than 90 years in prison if convicted on all charges.

Former Hollinger chief financial officer Jack Boultbee and former Hollinger general counsel Mark Kipnis each face 11 counts of wire fraud, mail fraud and filing false corporate tax returns. Peter Atkinson faces seven charges.

All four defendants pleaded not guilty. None of them testified during their trial.

Trial watchers not surprised

The fact that the jurors are having difficulty reaching a verdict is not a surprising development, given the amount of time that has transpired since the case went to the jury, said James Stribopoulos, an assistant professor of law at York University's Osgoode Hall.

"I think anyone watching the trial closely who knows anything about the criminal justice system can't be taken aback by this development," he told CBC News.

Stribopoulos said the question now is: how extensive is the disagreement among the jurors and which defendant does it concern?

Hugh Totten, a U.S. lawyer who has been monitoring the Black trial, said the jury's note is a common outcome in cases of this complexity involving multiple counts and several defendants.

James Morton, the president of the Ontario Bar Association, said the jury could find the accused not guilty of some charges, but guilty of others.

"It doesn't have to be a uniform decision, but it does have to be unanimous," he said.

Given Tuesday's events, Morton anticipates a verdict could come as soon as Wednesday.