Was Zarek responsible?

On a rewatch of Battlestar Galactica, and just got to Colonial Day in season 1.

One of the plot lines in the episode is the first and last appearance of Valance, who appears to be planning to assassinate Roslin. Zarek is seen as one of those most likely to benefit. Valance is captured and interrogated, but later found dead in his cell.

Shortly before this, Tom Zarek mentions ‘trying to find his friend’ to Ellen Tigh, who is keen to work with him, seeing him as a rising power in the fleet. He gives the name Valance, and it is implied that he was well aware of the plot.

Towards the end of the episode, Zarek tells Roslin that he didn’t kill Valance. Clearly he has nothing to gain by confessing if he was responsible, but equally there’s not much incentive for him to bring it up at all.

Is there any canon mention of who killed Valance?