The European Commission warned on Tuesday it could sanction member states that don’t follow EU quota rules for asylum seekers by opening infringement proceedings against them as early as next week.

The warning comes after the Czech Republic – which has protested quotas from the start – said it would not take in any more migrants, citing security concerns.

“We will specify our position on opening infringement procedures against the member states that have not relocated anyone at all or have not pledged any places for almost one year since we all decided to do it together,” Dimitri Avramopoulos, EU Commissioner for Migration and Home Affairs, told reporters.

Czech Interior Minister Milan Chovanec said on Monday his country would not take in any more migrants before the plan expires in September.

“The Government approved the suspension of this system for the Czech Republic because of the deteriorating security situation and the malfunctioning of the entire relocation system. The government also urged the Interior Minister to end all activities in these areas. This means that the Czech Republic will no longer take part in the relocation of migrants arriving in Greece and Italy,” he said.

The Czech Republic has only taken in a dozen migrants out of a quota of some 2,600, according to reports. Poland, Hungary and Slovakia have also refused to take part in the scheme.