AT&T and Verizon are dealing with an outage causing dropped phone calls across the US, seemingly affecting calls between customers of the two services.

According to a statement from AT&T spokesperson Jim Kimberly, “Our network is not experiencing a nationwide outage. There is a nationwide issue that is affecting the ability of some customers to complete calls between carriers. We are working closely with Verizon to determine the nature of the issue and what actions need to be taken.”

Verizon spokesperson Kevin H. King tells The Verge that the network is “operating normally” but notes that customers primarily in the Northeast and Midwest “are experiencing issues when calling or texting with customers served by another carrier.”

We still don’t know exactly when the outage started or what caused it. Verizon and AT&T charts on Downdetector suggest that problems may have started around 2PM ET. The Federal Communications Commission is also looking into the issue. “We’re aware of reports that consumers in multiple states are unable to make wireless calls and we are currently investigating,” the FCC writes in a post on X.

In February, a massive AT&T outage brought down service for thousands of customers nationwide. The carrier later apologized for the outage and offered a $5 credit to affected customers.