CHICAGO (CBS) — Four Macy’s employees were taken to hospitals after an aerosol can overheated and ruptured during an employee breakfast at the State Street store Friday morning.

Shortly before the store opened at 10 a.m., the Fire Department sent five ambulances to Macy’s at 111 N. State St., for a cooking accident in a kitchen area on the pedway level of the store.

The Fire Department said an aerosol can overheated and ruptured, creating a flash fire that extinguished itself. Four people were transported to hospitals with injuries.

One woman suffered serious facial burns. The other three employees suffered only minor burns.

“One of them had some burns to the face, which I can’t get into at this point, but that person was transported to [John H. Stroger Jr. Hospital of Cook County] in serious condition,” said Field Chief Paramedic Elliott Velez.

The employees were taking part in an employee pancake breakfast just before the store opened.

“Four associates were injured in an accident this morning during a cooking event before the store opened,” A Macy’s spokesperson said in an email.

No customers were in the store at the time, as Macy’s had not yet opened. The store opened at 10 a.m., and was operating normally.

Macy’s was cited by the fire department for improper storage and use of butane.