Echo during MSteam calls

Hello, We have MSTeams Meetings whereby some colleagues are sitting in a meeting room, one PC is used to connect to the network and external microphones/loudspeaker combinations are lying on the table. Other colleagues call in and are using headsets. When the colleagues that are calling in, are speaking there is a severe Echo , which makes the conversation very difficult to understand and which is also very painfull to the hears when you wear a headphone. The echo stops when the presenter in the meeting room puts his PC on mute. But that is not always suitable in a conversation. Is there a specific set-up that can be used to avoid this?