Fire alarm went off and the meeting was interrupted, the commissioner noted. This is always a serious issue, so the building needed to be evacuated, he added.
Zbogar confirmed the information while leaving the Berlaymont building in Brussels' European quarter. The minister is expected to give a statement after the meeting.
Rehn met Zbogar in the morning for talks, while Jandrokovic was to join them, when the fire alert forced them to evacuate.
Rehn said that a trilateral meeting was planned shortly and that the talks would continue.
Asked if a breakthrough in the talks is expected today, Rehn said that he would discuss the countries' responses to his latest proposal and future steps with the ministers.
According to Slovenian Foreign Ministry spokesman Milan Balazic the purpose of the meeting is to discuss different interpretations of Rehn's proposal.
While Croatia fully accepted the proposal, Slovenia sent to Brussels a number of amendments which it believes are vital for the protection of its national interests.
The European Commission headquarters were evacuated little more than a week after a blaze damaged the building and closed it down for several days.
This time, the alarm was reportedly set off by vapour from a hot water leak.