Cumbria County Council says it's waiting for the water level to drop further, before divers can carry out a full detailed structural inspection of Eamont Bridge.
So far, the visible damage and first inspection has been enough for the council to close the bridge to traffic, but says more detailed work is needed to assess the full extent of the damage.
If the damage isn't any worse than currently assumed, the council says it hopes to be able to repair it - but if more extensive damage is found, other options will have to be considered.
A Cumbria County Council spokesman said: “Until we are able to do full structural surveys we won’t know how long the bridge will be closed. We understand how frustrating that is and we are doing what we can to make the diversion work as smoothly as possible. We know that potholes are appearing and we will be making temporary repairs, but given the volume of traffic now using these single-track road that is less straightforward than it was. We appreciate people’s patience and would assure them that we want the bridge open as soon as possible.”