Boston police recovered 67 canisters containing nitrous oxide near Fenway Park on Friday, police said — which happened to be the same night that Phish was playing a concert at the Red Sox’ ballpark.

Officers observed a large group of people inhaling nitrous oxide from balloons “in an effort to achieve a high” before a concert, according to police, although which concert was not specified. (In addition to Phish at Fenway, Anberlin and I the Mighty were scheduled to play at the House of Blues that same night.)

According to police, the balloons were filled using the numerous canisters, and were then subsequently discarded on the street and sidewalk.