Up to 150 migrants reportedly try to storm the French side of the tunnel, causing further disruption and delays.
11:56, UK,
Channel Tunnel traffic has faced futher disruption after migrants tried to enter the terminal in Calais, followed hours later by a "technical fault".
The problems started at around 10.30pm local time after 150 migrants attempted to enter a restricted area of the tunnel, according to a Calais official.
The interruption to traffic going through the tunnel caused long queues of lorries to form on the M20 in Kent.
A Eurotunnel spokesman said the incident in Calais had affected freight traffic only, with passenger services running to a full timetable.
However, passenger services later faced delays of up to 90 minutes because of what was described as a "technical fault in the Tunnel which is in the process of being resolved".
Lorry drivers faced disruption and delays on both sides of the Channel and parts of the M20 were closed as police implemented phase two of Operation Stack.
Phase one involves closing junctions 11 (Hythe) and 12 (Cheriton) coastbound so lorries heading for Dover can park on the motorway.
When this part of the motorway is full police launch phase two and close junctions eight (Leeds Castle) and nine (Ashford West).
Kent Police tweeted: "Non-freight traffic now being allowed into Channel Tunnel terminal. M20 Junctions 11 to 12 no longer closed but delays likely. Check with operator if heading to Channel Tunnel as services disrupted."
The Highways Agency announced that the M20 heading towards Dover was closed between junctions eight and nine due to an "incident" but added it was expected to re-open from noon.
Ferry services are reported to be operating as normal at the Port of Dover.
More than 3,000 hauliers were parked on the M20 earlier this week after the closure of the Port of Calais crippled Channel sailings.
The chaos was sparked after MyFerryLink workers began a strike on Monday in protest at expected job cuts.
Some 3,000 migrants are currently camped out around Calais and are trying to cross the Channel into Britain.
France and Britain agreed in September to create a fund of €5m (£3.5m) per year to help Calais cope with the influx of migrants by reinforcing security around the port and the Channel Tunnel entrance.
Volunteers from the charity L'Auberge des Migrants say up to 50 new migrants were arriving every day at the camp, and there were not enough tents, blankets or food.
British travellers have been advised by the Foreign and Commonwealth Office (FCO) to keep vehicle doors locked in traffic and when unattended in Calais
