Suburban Hospital in Bethesda temporarily closed its emergency department to ambulance traffic on Labor Day after a technology failure knocked out systems across three Johns Hopkins hospitals.

The outage triggered what Maryland calls a "Code Black" at Suburban, Howard County Medical Center in Columbia and Sibley Memorial Hospital in Washington, D.C., on Monday, Sept. 7. Under state guidelines, Code Black means an emergency department "is effectively closed to EMS traffic due to unsafe conditions."

Suburban Hospital, the nearest major ER to Potomac, was among the facilities affected. Under Code Black, ambulances are diverted away from the affected emergency department to other hospitals.

The disruption began Monday afternoon, The Banner reported. By 5 p.m., Suburban and Howard County Medical Center had cleared the Code Black. Only Sibley Memorial remained under restricted status at that point.

Kim Hoppe, a Johns Hopkins Health System spokesperson, confirmed the cause was a network problem and said the system had been fully restored.

"We have restored full functionality. This was not a cyber-attack," Hoppe said in a statement.

Johns Hopkins did not disclose the exact cause of the network failure or say how long emergency services were curtailed.

The incident came four days after a separate, confirmed cyberattack hit two other Maryland hospitals. Luminis Health, which operates Anne Arundel Medical Center in Annapolis and Doctors Community Medical Center in Lanham, announced Sept. 3 that a cybersecurity breach had knocked its phone system and patient portal offline. That attack also forced some ambulance diversions.

The two incidents involved different hospital systems and are not connected.

The Banner reported that the Maryland Department of Emergency Management (MDEM) did not respond to a request for comment on Sept. 7. No follow-up statement from MDEM or Johns Hopkins about the cause of the outage has surfaced since.

In a medical emergency, call 911. Dispatchers route ambulances to the nearest available facility. Residents can check hospital ER status through the Maryland Emergency Department Advisory System at edas.miemss.org.