Hungarian authorities have closed Budapest's main rail station today after a weekend which saw record numbers of migrants board trains running through the country to Austria and Germany in a bid to find asylum.
One question raised by Hungary's decision though is whether it is in breach of Europe's Schengen agreement which allows for the freedom of people to travel through member states without having to undergo border checks.
What is the Schengen agreement?
It is an agreement that allows for passport free travel through 26 European states as participating countries have agreed not to impose border controls
Which countries are signed up to the agreement?
Austria, Belgium, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Italy, Latvia, Liechtenstein, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Slovakia, Slovenia, Spain, Sweeden, Switzerland.
Which countries are not signed up to the agreement?
The UK and Ireland have opted out of joining
Croatia and Cyprus are not members
Bulgaria and Romania are not part but are in the process of joining up
How could Europe's migrant crisis be putting the Schengen agreement at risk?
Refugees are meant to register in the first country they enter (under the Dublin Convention) but many migrants are using the Schengen agreement's lack of border controls to cross through Europe unnoticed, travelling from countries who are averse to giving them asylum to ones that will
According to German Chancellor Angela Merkel unless all European countries agree to share responsibility for refugees the agreement will be a risk as it will allow too many people to travel through Europe unchecked
According to British Home Secretary Theresa May allowing people to move freely through Europe without border checks is exacerbating the migrant crisis