Dover-Calais ferry sailings are operating normally again following a strike by French ferry workers, and more resources have been pledged for screening arrivals at Dover.
The Channel Tunnel had to be shut on Tuesday when the workers broke in and migrants attempted to board UK-bound lorries.
Eurotunnel said that its passenger and freight shuttles were running as scheduled through the tunnel while high-speed train company Eurostar was operating a full service from London through the tunnel to Paris and Brussels.
The ferry workers' action closed the port of Calais for a time on Tuesday, but the port is now open and Dover-Calais sailings are running normally.
Eurotunnel spokesman John Keefe said: "After we resumed services, we ran an enhanced freight service through the night to clear the backlog.
"We are systematically searching every truck that comes into the terminal on the French side to ensure it is clear of migrants before it enters the tunnel."
Eurostar had to cancel all services from mid-afternoon until the end of Tuesday, but services started on time again with the 5.40am, London to Paris train the first to depart.
More resources will be put into screening arrivals at Dover, Immigration Minister James Brokenshire has said, adding that extra French police officers are being deployed in Calais to deal with the problem.
The earlier travel problems came amid a worsening migrant situation near the Port of Calais where numbers camped there have swelled to more than 3,000 since April.
Aid workers have reported a "catastrophic" situation, with predictions that some 2,000 more migrants displaced from war-torn countries including Eritrea, Syria and Afghanistan could arrive over the summer.
Mr Brokenshire told the BBC: "It is hugely regrettable that we've seen these incidents occurring as a result of industrial action in France.
"We are putting additional resourcing into the port of Dover to enhance screenings and detections there so that we're looking at this on both sides of the Channel."
He added: "We have been advised the French authorities are sending further policing to deal with law and order issues, and we will be keeping in close contact with them in the hours ahead."
The deputy mayor of Calais, Philippe Mignonet, reiterated calls from French politicians for the border to be moved from northern France to Britain.
Mr Brokenshire said: "These deployments of additional border force resourcing at Coquelles around the Eurotunnel terminal and also from our work at Calais, buttressed by further support at Dover, is about maintaining that safety and security and the integrity of the border, which is our absolute focus."
Home Secretary Theresa May was given an assurance by her French counterpart that the authorities there "would do the job" in Calais, Mr Brokenshire said.
He said: "We maintain very close connections with the French government. The Home Secretary spoke to Bernard Cazeneuve, the French interior minister, last night to underline that sense of cooperation between the two governments.
"Clearly some of this is about policing and Bernard Cazeneuve said the French 'would do the job'."
He told BBC Radio 4's Today programme that the £12 million deal struck with the French in September last year was aimed not just at increasing security but about "communication with the migrants to explain what the real picture here is in the UK", countering some of the information given to migrants by people traffickers about what to expect in Britain.