German police fear only a fraction of illegal immigrants passing into EU territory are being caught after its border posts were abolished last month, according to Daily Mail.
Its Interior Ministry said 564 immigrants, most from Chechnya, have been caught since free movement was extended to the Ukraine frontier.
But police unions warned the true number is far higher, meaning thousands more could be heading to Britain since its border with Poland was scrapped.
Many of those caught had already applied previously for asylum in Poland and had not entered the EU after the Schengen Agreement was extended on Decemeber 21.
The EU`s own border agency says it is too early to draw conclusions.
"There`s been no new mass migration detected and the situation on a whole has been rather quiet," said Gabriele Hermani, a German Interior Ministry spokeswoman.
She said there had been no notable increase in illegal immigration or crime.
"We`re confident the reorganised federal police force (ex border patrol) will master the challenges," she said.
Some 6,000 police operate in mobile patrols in a 18-mile wide strip at the German frontier, randomly checking one in 2,000 vehicles.
The extension of the Schengen zone on Dec. 21 to nine more nations created an area of passport-free travel of 24 countries spread over 2,500 miles from Estonia to Portugal.
The enlargement brought in Poland, Slovakia, Hungary, the Czech Republic, Slovenia, Malta, Latvia, Lithuania and Estonia.
It is expected to boost business and tourism but brought accompanying fears of increased people-trafficking and crime.
But Interior Ministry officials said the numbers, which rose briefly in the final week of 2007, are similar to before enlargement.
They said the fact that illegal immigrants were caught showed the system works.
The issue has also stirred emotions in Austria.
Tabloid newspapers raised worries of a massive increase in illegal migrants and asylum-seekers but broadsheet dailies, public television and other media called the fears groundless.
Austrian Interior Minister Guenther Platter said he felt the debate had been hijacked for partisan politics.
"You have to take the public`s fears very, very seriously," Platter told journalists.
"It`s obviously a different situation when the border controls suddenly disappear.
"But I don`t see more seeking asylum ... and I don`t see an increase in crime."
Figures from Poland`s border agency headquarters show the number of illegal immigrants stopped on the EU frontiers under Polish jurisdiction - with Russia, Belarus and Ukraine - was down nearly 50 percent in the first three weeks after Dec. 21.
"Too little time has passed to identify any particular trends," said Michal Parzyszek, a spokesman for the EU`s external borders watchdog FRONTEX.
"My guess would be that if any surge has occurred, it would be between the nine new Schengen states and the previous members.
"Some immigrants could have been hiding in Poland before December 21 and are now trying to get to other parts of the EU."
In Prague, police said that there had been no extraordinary changes since joining Schengen.
Czech officials did say, however, they had also intercepted a number of illegal immigrants from Chechnya.
They were caught trying to travel from Poland to Austria via the Czech Republic.
In Brussels, the European Commission said the expansion of the Schengen zone was working fine so far.
Commission spokesman Friso Roscam Abbing said, however, it was it was too early to tell if there had been any increases in illegal immigration.