Wales fans travelling to France to watch their team face Belgium faced hours of travel delays on Friday.
Earlier, Eurotunnel LeShuttle tweeted that commuters faced a four-hour wait, although three extra trains were put on to try to help the problem.
Fans reported waiting up to five hours ahead of Wales' quarter final match in Lille.
Some fans called for the start to be delayed, but Uefa said the game would go ahead as scheduled.
The Football Supporters' Federation Cymru tweeted that the voucher exchange system in Lille has been extended until 21:45 local time (half time) so fans who were late could still exchange their vouchers for tickets into the stadium.
There were some very minor skirmishes ahead of the game, with riot police deployed and the trouble quickly stopped.
The police the BBC spoke with believed the fans involved were not from Wales.
Broadcaster and singer Cerys Matthews was among those stuck at the Eurotunnel and called the situation a shambles in a series of tweets.
She said she faced a five-hour delay but was eventually able to get to the match - just in time for the anthem.
Eurotunnel tweeted the delays were "due to cancellations caused by technical problems".
Public affairs director John Keefe said: "We understand how important this game is and we will get as many people away as possible."
Wales fan Rod Woodward described "chaotic scenes" at the terminal, with fans in tears.
Andrew Reid, from Newport, offered £200 to swap his train ticket for an earlier time, but believed he and his four friends will miss the game.
"We're having a nightmare," he said. "We've just realised we might not even make the game. We've paid £180 each for a ticket, then there's the transport and accommodation."
The game has been billed as the "biggest day in Welsh football history", with the team never previously progressing this far in the tournament in its current format.
The head of Welsh police in France said reports Belgians would heavily outnumber Welsh fans were "wide of the mark".
With the Stade Pierre Mauroy in Lille 10 miles (16km) from the Belgian border, there were reports more than 100,000 Belgium fans could descend on the city.
But Supt Steve Furnham dismissed the suggestion, and said 20,000 Belgian supporters without tickets are expected.
As the fan zone only holds 20,000, and with tickets being "scarce", he told BBC Radio Wales it was an issue they were taking into "consideration".
Wales fans said they were going into the game with "hope" against a side ranked second in the world by FIFA.
In the last three matches between the two sides, Wales have won once and drawn twice, and Welsh fans remain upbeat.
Philip Richards, 69, of Mountain Ash, said he thought it was possibly the most seminal game for Wales football fans.
"There's no reason, with the team they have got, that they couldn't produce the quality required," he said. "The question is whether they will."
Wales have been drawn as the home team and will play in red; if they win, they will play Portugal in Lyon on 6 July.
Alcohol restrictions remain in place in the city, with pubs, bars and clubs closing at midnight after the game.
On Thursday, the Football Supporters' Federation Cymru warned fans against buying tickets from touts and advised them to get to the fan zone early to avoid missing out on getting in.
Lille is also short on accommodation, due to increased demand in relation to centenary commemorations of the Battle of the Somme.