The EC contacting work safe would demonstrate an attempt to ensure safety. I think it should be proactive by also directly contacting the builders telling them to secure the balconies and also by putting notices on the doors of every unit with a balcony.
It could also be useful to rope off the area below the balconies if the builders have not done so (as they should have). The danger is not just to a person falling but also to anyone underneath any kind of falling object.