AZ confirmed there were no reported injuries.
General manager Robert Eenhoorn told a news conference: "This surprised all of us.
"We've very shocked but particularly happy there was no human suffering. In the coming days, we'll conduct a review with experts in this field. Only when that investigation has been done can we elaborate on this matter.
"No matches will be played in the stadium if the situation is not safe. As soon as more is clear about our upcoming matches, we'll report it as soon as possible."
AZ were due to play Mariupol in a Europa League qualifying match next Thursday and an Eredivisie game against Groningen three days later at the stadium.
The ground was built in 2006 and has a capacity of 17,000.