We have a small container Masjid

In our company, we have a small mosque made of a container with a small Meenar at its one corner and a Mehrab for the Imam. Normally, 2 times prayer in a day  is performed here. 30-35 people can pray at a time. Juma not performed. We don’t know whether it is a permanent or temporary mosque, because we don’t know what was the actual Niyyat / intention of the person (May Allah Bless him) when it was placed, whether to be a permanent or temporary mosque. In our opinion, it might only be placed just to fulfill the needs of people without any Niyyat. But, we are not sure. However, in our company’s official drawing, a Mosque / Prayer room is shown at this same place where this mosque container is placed. Now, our non-Muslim management wants to construct an office over this container mosque without touching it. Only the small Meenar may be displaced. Actually, they will install the pillars / column supports just outside the mosque and then prepare an office over the roof of mosque container. Is it allowed?  Please reply soon as they have started preparation works.