Party City is closing 45 stores this year after struggling to find enough helium to fill its balloons, the company announced Thursday.

Balloon sales at the New Jersey–based party-supply company fell amid a global helium shortage, Party City said in a statement.

The company did not say which of its approximately 870 stores in the US and Canada would be shuttered, but the closures will take place throughout the year.

Party City usually closes only 10 to 15 stores a year. However, the helium shortage "negatively impacted our latex and metallic balloon categories," the company's CEO, James M. Harrison, said in a statement.

Party City made the decision to close more stores than usual to "help optimize our market level performance, focus on the most profitable locations and improve the overall health of our store portfolio," Harrison added.

The company has signed an agreement for a new source of helium that might provide its stores with more quantities of the gas for the next two and a half years. But in a conference call with Wall Street analysts Thursday, Harrison acknowledged the unfortunate timing of the helium shortage in May — "a big season for balloons" because of graduations, CNN reported.