Barcelona's home game against Eintracht Frankfurt looked almost as if it was an away game.
Between 20,000 and 30,000 Frankfurt fans managed to get into the stands, buying tickets off Barca socios. The visiting crowd chanted and supported their team, shocking Blaugrana fans.
The team was also affected by the ticketing chaos.
"We have not talked yet about what happened in the stands in the last game," Xavi said at a presser.
"An investigation has been opened, and I hope that measures will be taken so that it does not happen again.
"As soon as the results of the investigation is announced, we will be informed of it, and the media as well. What happened is our fault.
"I had a bad feeling after we left the hotel for the Frankfurt game. There were people throwing things at us, and we had to enter the stadium through a different gate. Then we conceded the early goal, I had a negative feeling.
"Barcelona fans supported us in the past matches, they encouraged and supported us even after we conceded goals. But that did not happen in the last game."
