The tool has been in beta since January, but the pilot programme is ending, and the company is likely to launch a freemium version of the interoffice network by the end of the year, Re/code reported project head Julien Codorniou as saying.
Facebook has been using a version of Facebook at Work internally for years.
More than 100 companies are using Facebook at Work as part of the beta. Many of those companies are just now starting to expand the product internally.
Heineken, a leading lager beer company, for example, has been testing the product with just 40 of its top executives, but plans to expand Facebook at Work to all 550 US employees by the end of September.
Linio, a Latin American e-commerce company, is expanding the product internally from 200 to 2,000 employees by the end of the month.
Facebook may cash in on the "familiarity". "If somebody comes into the company, they know how to use this tool from day one. So training cost is zero. That's important," Ryan Holmes, CEO of Hootsuite, which is part of the beta group, was quoted as saying.
Facebook will need to convince employers that green-lighting Facebook use among the staff won't result in a loss of productivity.
"It is unrealistic that organisations try to lock people out of social. It is like telling people that they can't have their own personal phone," Holmes noted.