Dog Door Security - Please Help

[briansgooglegroupemail@xxxxxxxxx]

I have a dog door that medium sized adult can squeeze through.  Well
the other night a medium sized adult tried to squeeze through it.  I
woke up before the person was in the house and turned all the lights
on.  By that time they had already jumped the fence.  In any event,
this makes me very nervous.

The dog door is in a small laundry room which has a pet immune motion
detector in it.  The motion detector did not go off because the person
had not yet stood up.  I don't think they had fully entered the room.
In any event, what besides a motion detector can I do to secure this?
Frankly, I am considering boarding it up and living without the dog
door.  But other suggestions would be greatly appreciated.