Four Democratic leaders on the US House of Representatives Energy and Commerce committee on Monday wrote Alphabet Inc's Google and Ascension Health demanding briefings by December 6 on how patient data the hospital chain is storing on the cloud is used.

Google's cloud computing unit said last week that it has incorporated industry standard security and privacy practices into its deal with Ascension, and that none of the data is being used for advertising purposes.

But House Energy Chairman Frank Pallone Jr. along with members Anna Eshoo, Diana DeGette and Jan Schakowsky, said in their letter that questions remain about what data exactly is stored with Google, which Google employees have access to the data, and to what extent patients were informed about the companies' agreement.