Hundreds of Verizon outages were reported in the Chicago area Monday morning, and thousands more across the country.

According to the website Downdetector, reports of Verizon outages in Chicago started around 7:15 a.m. Monday. At 9:15 a.m., a spike of more than 700 outages was reported in the Chicago area, the web page showed.

According to the site, more than 20,000 Verizon outages were reported nationwide as of 9:15 a.m. By 9:30 a.m., that number had risen to more than 70,000, the site showed.

An outage map from Downdetector Monday showed Verizon outages in several other cities, including Indianapolis, New York City, Atlanta, Cincinnati and Omaha.

Dozens of comments on Downdetector from users said their phones were showing “SOS” mode on and off.

As of 9:30 a.m., Verizon had not posted about the problems on social media. However, the carrier responded to tweets from multiple users reporting issues.

“We understand the importance of staying connected and would like to see what’s happening,” said several responses from Verizon.

Verizon did not immediately respond to NBC Chicago’s request for comment.

What is SOS mode?

According to Apple, that message appears when “your device is not connected to your cellular network,” but it also means you can make emergency calls over other carriers’ networks.

The feature is only available in the US, Australia and Canada.

“If SOS appears in the status bar of your iPhone, it means a cellular network is available for emergency calls,” the company says.

Anyone who calls with SOS automatically goes to a local emergency number and shares their location with the emergency services.

Users can also set their phone so that after they make an SOS emergency call, their phone will alert emergency contacts with a text message with their current location – and update those contacts if that location changes.

“On iPhone 14 or later (all models), you can even use Emergency SOS via satellite to text emergency services when cell and Wi-Fi coverage isn’t available,” Apple states.