Chinese hackers targeted data from phones used by former President Donald J. Trump and his running mate, Senator JD Vance of Ohio, as part of what appears to be a wide-ranging intelligence-collection effort, people familiar with the matter said on Friday.

Investigators are working to determine what communications data, if any, was taken or observed by the sophisticated penetration of telecom systems, according to these people, who spoke on the condition of anonymity to describe an active and highly sensitive national security case.

The type of information on phones used by a presidential candidate and his running mate could be a gold mine for an intelligence agency: Who they called and texted, how often they communicated with certain people and how long they talked to those people could be highly valuable to an adversary like China. That sort of communications data could be even more useful if hackers could observe it in real time.

The Trump campaign team was made aware this week that Mr. Trump and Mr. Vance were among a number of people inside and outside government whose phone numbers had been targeted through the infiltration of Verizon phone systems, the officials said.