Police forces across several states, from Nebraska to Nevada, reported their 911 phone lines are down - causing chaos for those needing emergency assistance.

Cities as big as Las Vegas, as well as the entire state of South Dakota and locales in Texas and Nebraska announced the outages on Wednesday night.

Officials in South Dakota, Nevada and Las Vegas said 911 services had been restored, but without identifying the cause of the failure. 

The Department of Homeland Security has warned, of increased risks of cyber attacks on 911 services as they have migrated to digital systems based on Internet Protocol standards. 

Several cyberattacks targeting 911 systems have taken down the services in recent years, one of which, in 2017, paralyzed 911 centers in more than a dozen states. 

Authorities asked callers not to test out the phone line while they try and get service back up

Cities as big as Las Vegas, as well as locales in South Dakota and Nebraska have both announced the outages and have posted administrative numbers as alternates

In Las Vegas specifically, no estimate was initially given after an outage wiped out landline and mobile phones connectivity to the crucial 911 number. 

Authorities asked for callers not to test out the phone line while they try and get service back up, amid fears that unreported crimes may be taking place. 

Nearby Henderson, Nevada was also facing a down 911 - but various other emergency services were still running. 

The entire state of South Dakota, Dundy County, Kearney County, Howard County and Fremont, Nebraska, as well as Del Rio, Texas were also affected. 

The emergency mobile number to get a hold of police, ambulance, and fire services was not connecting to call centers for many hours throughout the night. 

Police urged the public to call alternative numbers if they needed help. 

In South Dakota, one county did say that text messages to 911 did appear still be going through. 

Others suggested that members of the public needing help ought to call 911 on a mobile device, and wait for the service to call you back. 

In Vegas and South Dakota, police announced just after 10pm local time that service was restored following a three hour outage.