SEIV: Attacking a mine deploying convoy

[Beorne]

I'm Playing a multiplayer game with synchronous turns (obviously).
A player is attacking my sectors me with a ship fleet full of mine lsyers. I have a stronger fleet than he but with the capacity to remove only 52 mines/turn.
The enemy is invading my territory so I can intercept him. giving the fleet the attack order on his fleet.
My fear is that he commands to advance some sectors AND lay mines (is possible?). When in the same turn I intercept him I stumble on the mines. Is it possible a situation like this? If go over a sector where he is in the same turn laying mines what does happen firs? My arrival (and the upcoming battle) or the mine laying?
Sorry for the convoluted question ...