This work investigates the causal relation as it is expressed in informative texts. Causal relations are viewed as important because of the dynamic dimension they bring to a domain model. Thorough study of a corpus leads to distinguish two prominent classes of indicators of the causal relation: conjunctional phrases, and verbs. This paper identifies multiple knowledge-rich patterns within each class and studies their usage, frequency and noise. Results from this manual investigation informs a discussion on the feasibility of automatic extraction of the different forms of expression of the causal relation.