Tenant liability of a pre-installed appliance

Last week, we received a note from our downstairs neighbour regarding stains on his kitchen ceiling. We checked the kitchen in our flat and did not see any visible signs of a leak on the surface. On Sunday, the washing machine stopped working. When we pulled it out and lifted the lino, we noticed significant damp underneath in the area around the washing machine. There were also some mould stains on the lino and on the concrete , which suggest that water may have been accumulating in that area over time. The machine itself did not have water in it when it broke, so there was no leak visible on the lino surface — the damp seems to have been underneath. The washing machine was already in the flat when we moved in and the agent asked us if we'd like to keep it as a gesture of goodwill from the landlord. We had not previously moved it or tampered with it. When we pulled it out, it looked like the hose may not have been fully secured, as it appeared slightly loose, which could explain why water had accumulated under the lino over time, but that would've been like that since it was installed, nothing that we could've done/moved to cause the drip.

Now we reported it immediately and mentioned everything above and the agent suggested that we might be liable for the repairs if it turns out that the washing machine caused the leak. In the meantime, the downstairs neighbor told us that the boiler from the apartment downstairs has broken down and the tenant doesn't have hot water/heating. How can we be liable of such damage just for accepting a pre-installed appliance? We have a contractor coming to inspect it this afternoon, but apparently we will be liable for the call out costs as well if it proves out to be the washing machine