A migrant has died on a freight shuttle trying to reach Britain, Channel Tunnel operator Eurotunnel said as it renewed calls to end the crisis in Calais.
The incident on the French side of the Channel happened at around 5.30am UK-time (6.30am French time), a spokesman said.
Freight traffic was disrupted but there were also delays to passenger services following the incident near Calais.
A Eurotunnel spokesman said: "At 5.30am the presence of migrants was reported on a freight shuttle just entering the tunnel.
"Safety procedures apply automatically if there is any human presence in the tunnel, therefore the train was brought to a controlled stop and the overhead power was cut.
"The French police conducted a search, in the process of which they found a migrant who they declared deceased a short while later.
"The police have cordoned off the area until 11.30am French-time. Eurotunnel deplores the fact that this tragic incident has happened.
"Eurotunnel once again calls on the governments to end the migrant crisis, and full services through the Channel Tunnel will resume as soon as possible."
Details about the age, sex and nationality of the migrant have not been revealed.
It is the second migrant fatality to take place in as many weeks following the reported death of an Eritrean while trying to get on a train at Coquelles last month.
Today's incident came days after around 150 migrants caused delays and cancellations when they tried to storm the Channel Tunnel terminal in France.
Kent Police said delays were building around junction 11a of the M20, where lorries are queued as part of Operation Stack when cross-Channel services hit disruption.
The migrant crisis in Calais has escalated in recent months, with around 3,000 people displaced from countries including Eritrea, Syria and Afghanistan setting up camp near the port.
Last week more than 3,000 truckers had to queue for several days in high temperatures on the M20 following a wildcat strike by ferry workers in France.
Industrial action by ferry workers this summer has come on top of the problems faced by hauliers with migrants desperately trying to clamber on board their HGVs to the UK.
French authorities have faced claims they are not doing enough to safeguard lorry drivers from intimidation, violence and attempts by migrants to climb on.
The Road Haulage Association (RHA) has suggested deployment of the French military to boost security in Calais amid fears that a fatality could occur.
The Fresh Produce Consortium estimates that £10 million of fresh fruit and vegetables have been thrown away since the start of the year as a result of the problems in Calais.
And Port of Dover officials said last week's ferry strike cost the UK economy £1 billion.
They have joined calls for "robust contingency plans" to be introduced to ensure the port - a £100 billion trade route - can work unimpeded by others.
Home Secretary Theresa May and her French counterpart Bernard Cazeneuve last week agreed to increase the joint intervention fund to improve security around the port and the Channel Tunnel.
French aid workers have reported a "catastrophic" situation, with predictions that 2,000 more migrants could arrive over the summer at the camp, dubbed Jungle II.
Volunteers from L'Auberge Des Migrants say up to 50 new migrants are arriving every day at the camp, and there are not enough tents, blankets or food.
Dover Conservative MP Charlie Elphicke has said the problems underlined the need to consider expanding the port at Dunkirk, 45 miles from Calais.