The wireless carriers' US networks are secure and the companies are working with law enforcement and government officials following the attack.
An AT T spokesperson said: "We detect no activity by nation-state actors in our networks at this time. Based on our current investigation of this attack, the People's Republic of China targeted a small number of individuals of foreign intelligence interest."
Verizon's Chief Legal Officer said in a statement: "We have not detected threat actor activity in Verizon's network for some time, and after considerable work addressing this incident, we can report that Verizon has contained the activities associated with this particular incident."
Verizon added that an independent cyber security firm has confirmed the containment.
Last week, US officials added a ninth unnamed telecom company to the list of those compromised by the Salt Typhoon hackers.
Chinese officials have previously described the allegations as disinformation and said Beijing "firmly opposes and combats cyber attacks and cyber theft in all forms".