After removing a mongos instance by force, I noticed that its information remains in the config.mongos collection. After a throughout search I found NO useful documentation explaining how to remove a mongos instance. The only option left is to manually remove that data like this:
mongos> use config
switched to db config
mongos> db.mongos.remove({ _id: "62-62-udp-1:6601" })
WriteResult({ "nRemoved" : 1 })
mongos>