Donald Trump and JD Vance's phones have been hacked by China ahead of the upcoming presidential election.
Investigators are looking into whether the hackers managed to access communications data from their personal cellphones, The New York Times reported on Friday.
Information on who the Republican candidate, and his running mate, have communicated with ahead of the election could provide Beijing with valuable intelligence.
If China has obtained such details, it would give its spies an insight into whom to target as part of any influence campaign.
Officials said the Trump campaign was made aware of infiltration into the Verizon phone network.
The hack also targeted a number of people inside and outside of the US government.
Trump has been targeted by a number of malign foreign activities before, including an assassination threat and influence campaign from Iran.
Iranian hackers have repeatedly targeted Trump's inner circle with phishing emails to get access to secret campaign documents and communications.
It is not known whether the Chinese hackers were able to read text messages, especially those sent through encrypted messaging services.
Trump's campaign has not directly addressed the reported hacks against the presidential nominee and his running mate.
But a spokesman for the former president did blame the White House for allowing a foreign adversary to target the election campaign.
Earlier this year, security officials detected a Chinese-affiliated hacking group, Salt Typhoon, inside the country's telecommunications system.
Investigators more recently discovered they were targeting specific cell phone numbers.
It is not yet known whether the hack has culminated in a genuine national security threat.