This paper addresses the challenge of integrating a dialog system with an ITS created for supporting procedural training in a 3D virtual environment. To this end, we first describe the desired features of the dialog to be provided to students in such system. Then, we explain some technical issues of our proposal such as the architecture; the design of the dialog manager; and the construction of the answers to the students' questions by leveraging an ontology related to the virtual world. Next, we present a pilot study with students to validate our approach. In this pilot study, we utilized a prototype that encompasses a 3D virtual laboratory. In the last seven years, students have used this virtual laboratory to perform a practice guided by an automatic tutor without dialog capacity. So, the evaluated prototype represents an extension of this automatic tutor that aims to give it the dialog capacity in the context of the practice.