(CNN) - The National Security Agency pulled 534 million records of phone calls and text messages from American telecommunications companies last year.
That's three times what it looked at in 2016, according to the office of the Director of National Intelligence, which compiled the report.
An official there says it's not clear why the number rose so sharply.
It could be because of increases in the number of phone accounts people of interest are using or changes to how the industry creates records.
The data pulled by the NSA includes who users contacted and when, but not the contents of those conversations.
The agency continues to collect significant amounts of data, but it's still way down from when it operated in secret.
Before its activities were outed by Edward Snowden in 2013, the NSA collected billions of records every day.
Copyright 2018 CNN. All rights reserved.
