Check around foundation. You say you have deck, so check under there (next to foundation or where connects to house). They only need a hole size of golf ball.
Set rat traps to kill them. The plastic ones are easier to set than old fashion ones.
Check along rain gutters that go to roof (could climb up them). Any posts next to house.
Hi and thanks for that advice. The deck is on the upper level but they could just run up the steps to get to it. We saw them going inside the downspout, which I guess is how they got access to inside the soffits. There are neighbour's trees beside the house with overhanging branches on this side, which they could jump on the roof or the gutters. We can't access the attic ourselves to check up there so we will leave that up to the experts.