Members of the Energy and Commerce Committee of the US House of Representatives sent the letters on Monday.
With recent media reports raising concerns about misuse of user data, the lawmakers sought information from the two companies on third-party access to consumer data, collection and use of audio recording data as well as location information via iPhone and Android devices.
In their letter to Alphabet's Page, the lawmakers pointed to reports that suggested that Google permitted third parties to access the contents of users' emails, including message text, email signatures, and receipt data, to personalise content despite an announcement in June 2017 in which the search giant said it would stop scanning Gmail for advertisements.
The Wall Street Journal last week reported that despite assuring users to "remain confident that Google will keep privacy and security paramount", it still allowed some third-party organisations to scan through Gmail accounts.
In their letter to Apple's CEO, the lawmakers asked if people's iPhones collect audio recordings without their consent and if Apple could "control or limit the data collected by third-party apps available on the App store", Fortune.com reported.