Temporary cage set up

[Kimmy1606]

I am looking for some advice for my guinea pig cage. We have a temporary guinea pig set up whilst my dad builds a new one for my guinea pigs. My dad has made a wooden ramp to sit inside this temporary cage and one of the guinea pigs will not stop chewing and eating the wood. It has only been in the cage for 1 hour but I wanted to check that any wood is ok to use before we leave it in for any longer?
I have attached some pictures of the set up.
Thank you in advance

 

[Piggies&buns]

Not all woods are safe
What wood has been made out of?

 

[Kimmy1606]

It is made from pine along the sides and plywood at the bottom. They have no way of chewing the bottom though so it is only the pone that is a worry really. Thanks for your help