Amazon has expressed interest in acquiring business messaging company Slack, sources familiar with the situation have attested.

Representatives of Bloomberg were told of talks between the two companies, although both Amazon and Slack declined to comment.

Slack’s valuation could reach as high as $9 billion, should a deal between the companies proceed. This past April, Slack was valued at $3.8 billion, when it reached a $200 million funding goal. Total dollars raised in the company’s three-year history surpassed $540 million at that time.

Slack, an enterprise-level messaging service, has promised customers a reduction of almost 50% in internal emails. It also claims to promote effective teamwork through the use of team channels, direct messaging, and phone or video conference services. Currently, the company boasts such high-profile customers as NASA, Samsung, LinkedIn and eBay. Slack’s penetration into Fortune 500 companies is estimated at 77%.

Slack, which offers a free basic account for users, currently has approximately 5 million daily average users, 1.5 million of whom have upgraded to a paid account with additional features.

The service recently debuted an enterprise-level version of the application, which was upgraded to include security, compliance, and additional collaborative features. Last month, it added screen sharing capabilities to Slack video calls, allowing a member of a Slack team call to share their computer screen in real time, automatically disabling the camera feed during sharing and restarting the camera feed when sharing ends.

In March, when Slack began expanding its board of directors by adding its first independent board member, CEO Stewart Butterfield said that an IPO for the company was years away, although management is “trying to run the company so that we’re ready to go public, not because we are going to necessarily. But because there is a lot of good discipline there, a lot of building of internal controls and a method of governing the business that is important.”

Internal controls and an eye to future development, and discipline, could only serve to make Slack a more attractive option for acquisition by a larger technology company.

The acquisition of Slack may be Amazon’s answer to Microsoft’s general release of Teams, an Office 365-compatible workspace chat application that has been seen as a major competitor of Slack.  Google is also rumored to be upgrading its Hangouts application to provide the same types of services offered by Slack.