T-Mobile US Inc.’s network was among those recently breached by Chinese hackers in an attack on multiple telecommunications companies.

T-Mobile has emerged as one of the victims in a recent large-scale cyber-espionage operation, reportedly tied to China, according to The Wall Street Journal. The hackers, believed to be a part of a group called Salt Typhoon and suspected to be connected to Chinese intelligence,

The carrier joins a growing list of known victims, including AT&T and Verizon, of the major Chinese spying operation.