Summarize the following:
Other people might have seen something. Visit your neighbors and ask if they know anything about the situation. Check whether they know where the owner is and how to contact them.  By talking to your neighbors, you also spread the word that someone might be in the house illegally. Not all squatters are dangerous, but your neighbors should nevertheless be advised of who is there. If a neighbor has seen something, have them write down notes about who they saw and when. Ask them to describe the squatters, if they can. You’ll need to notify the police and the building owner, but you should have some evidence to share with them. This evidence will be useful if the owners need to sue to evict the squatters. Do the following:  Take detailed notes of who you see coming and going from the property. What do they look like? How many people are there? What dates have you seen them? Photograph the building if you see broken windows or graffiti. There might be an innocent explanation for why someone has been in the property. For example, the people you see going in and out might be the lawful owners. Ask the people you encounter who they are and why they are there.  You are not required to speak to the squatters, and you shouldn’t if you are scared of them. It’s enough to record what you have observed and then call the appropriate people. If you’re scared, another option is for a group of neighbors to go talk to the squatters. There’s safety in numbers.
Talk to your neighbors. Document the squatting. Speak to the squatters if you aren’t afraid.