SHERBROOKE, Que. -- Jurors in the Lac-Megantic criminal negligence trial have completed their sixth day of deliberations after telling the judge they had hit an impasse.

Quebec Superior Court Justice Gaetan Dumas convened the eight men and four women in the middle of the afternoon after receiving their letter.

Dumas sent the jurors back and asked them to try once more to reach unanimous verdicts.

The jurors are deciding the fate of Tom Harding, Richard Labrie and Jean Demaitre.

The three are charged in connection with the July 2013 tragedy in which 47 people were killed when a runaway train carrying crude oil derailed and exploded.

All three accused can be found guilty of criminal negligence causing the death of 47 people, while jurors have the option of convicting Harding on one of two other charges: dangerous operation of railway equipment or dangerous operation of railway equipment causing death.