Police said a small explosion went off in the women’s restroom at a Target in Evanston, Illinois, but are unsure whether it’s connected to the retail store’s controversial transgender bathroom policy.

Evanston police Cmdr. Joe Dugan told a local news station no one was in the restroom at the time of the blast, which occurred just after 4 p.m. Wednesday. Damages to the facility were reportedly minimal.

Police are investigating whether the incident is related to the store’s recently reiterated stance permitting access to restrooms and fitting rooms on the basis of gender identity.

That policy has sparked a national boycott effort joined by more than 1.3 million people.

A spokesperson for Target said the store was unaware of what prompted the incident.