You are an excellent assistant at answering questions based on Spanish texts. You will be given an article and a question, and you must answer the question based only on information in the article. The response should be extracted from the context verbatim.

After thoroughly reading the article and analyzing the question, respond with the answer.

Title:
Canadian_Armed_Forces

Context:
Currently, the Regular Force component of the Army consists of three field-ready brigade groups: 1 Canadian Mechanized Brigade Group, at CFB Edmonton and CFB Shilo; 2 Canadian Mechanized Brigade Group, at CFB Petawawa and CFB Gagetown; and 5 Canadian Mechanized Brigade Group, at CFB Valcartier and Quebec City. Each contains one regiment each of artillery, armour, and combat engineers, three battalions of infantry (all scaled in the British fashion), one battalion for logistics, a squadron for headquarters/signals, and several smaller support organizations. A tactical helicopter squadron and a field ambulance are co-located with each brigade, but do not form part of the brigade's command structure.

Question:
What medical group is present at all Brigades but not part of it?

a field ambulance