Facebook is reportedly testing a new search tool that could bring back posts thought to have been lost long ago.

Facebook is testing the feature in its mobile app, and it lets people use keywords about people or events to look through old posts from friends, according to Daily Mail. Users with mobile devices can access any content that they could see in the past through friends or pages they followed.

Facebook said the tool serves as an "improvement to search and mobile," adding that the only pictures that will be available will be those that the user allows to be viewed on their privacy settings.

Facebook CEO Mark Zuckerberg has been looking to expand the capabilities of Facebook Search, saying in the company's Q4 2013 earnings call that the site would benefit from giving users the chance to search through Facebook's content, Business Insider reported.

"There are more than a trillion status updates and unstructured text posts and photos and pieces of content that people have shared over the past 10 years, and indexing that was a really big deal, because as the number of people on the team who have worked on web search engines in the past have told me, a trillion pieces of content is more than the index in any web search engine," Zuckerberg said.

Having faced privacy concerns in the past regarding content that users thought would be hard to find, Facebook will give users more control over their settings, Business Insider reported. Users now also have the option to find out why they receive certain ads.

However, the company is still receiving criticism over its handling of data, especially with its Messenger application, which has received criticism due to customers wanting to know how Facebook will enact its terms of service.

The app lets Facebook send texts and make calls on the user's device, and can also find accounts and read contacts. An additional feature in the app is its ability to access and edit the user's read and received text messages, Daily Mail reported.

Certain permissions give Facebook's app other abilities, such as directly calling phone numbers, taking pictures and videos, downloading files without notification, and changing network connectivity.

"Keep in mind that Android controls the way the permissions are named, and the way they're named doesn't necessarily reflect the way the Messenger app and other apps use them," Facebook wrote in a blog post.

The new search tool is the latest among Facebook's newly released features, including a "satire" tag feature designed for preventing users from being tricked by satirical websites.