A mass cellular outage across the United States contributed to “many” 911 centers in Massachusetts getting flooded with calls from people trying to see if the emergency system worked, the Massachusetts State Police said Thursday morning.

Major cellular providers were reporting issues, including AT&T, Cricket Wireless, Verizon, T-Mobile, and others, according to data from Downdetector, which tracks service. AT&T alone had more than 74,000 reports of outages from customers with issues starting around 3:30 a.m., the data showed.

“Some of our customers are experiencing wireless service interruptions this morning. We are working urgently to restore service to them. We encourage the use of Wi-Fi calling until service is restored,” the phone carrier said in a statement.

Massachusetts state police said centers were “getting flooded” with phone calls from people trying to see if 911 service worked from their cell phone.

“Please do not do this. If you can successfully place a non-emergency call to another number via your cell service then your 911 service will also work,” the state police said in a statement just after 9 a.m.

The state police said they were in contact with AT&T and were “monitoring the outage situation involving some commercial cellular carriers.”

“Some carriers have coverage, but if you need to call 911 and cannot do so, use a landline if possible until situation is resolved,” the state police said.

Cricket Wireless had more 12,700 reports of outages from customers just after 9:15 a.m., according to Downdetector. T-Mobile had just over 1,800 after 9:15 a.m.

But T-Mobile said it was not experiencing an outage.

“Our network is operating normally. Down Detector is likely reflecting challenges our customers were having attempting to connect to users on other networks,” the company said in a reason.

Materials from the Associated Press were used in this report.