Consequences of skipping a Spanish toll gate?

[ensnare]

We just returned from a road trip from Roscoff to Bilbao, but unfortunately, we accidentally missed the last toll road leading to the Bilbao ferry, which I believe is called the AP-8. It seems that the cars in front of us had a tag, and we mistakenly followed them, thinking it was the entrance to the ferry terminal. As a result, the lights flashed and an alarm went off—oops!

Now, I'm unsure about the consequences of this oversight. Some websites suggest a 100 euro fine, while others mention a grace period if we manage to contact the road's owning company. I've tried searching for their contact details online, but I haven't had much luck so far.

If anyone has any information on how I should proceed, I would greatly appreciate it. I'm hoping to get in touch with the company and simply pay the fee, including any administrative charges that may apply.