Microsoft said Monday it would start reopening its headquarters offices next week and implementing a "hybrid workplace" that brings back more employees around the world after a year of remote work during the pandemic.

The move is the first formal reopening plan to be announced by Big Tech firms which have kept most employees on remote work where feasible during the past year.

"Our approach is data-driven and research-backed," said a tweet from the tech giant which employs some 160,000 people worldwide.

"As of today, after over a year in which most Microsoft employees have worked remotely, several of our work sites around the globe have reached a stage that meets or exceeds government requirements to accommodate more workers,"  executive vice president Kurt DelBene said in a blog post.

"Currently, Microsoft work sites in 21 countries have been able to accommodate additional workers in our facilities -- representing around 20 percent of our global employee population. On March 29, Microsoft will also start making this shift at our Redmond, Washington, headquarters and nearby campuses."

DelBene said the hybrid model would allow flexibility in allowing some employees to continue remotely while bringing back some to the office when conditions permit.

"At each of our global work sites, the hybrid workplace model strikes a balance, providing limited additional services on campus for those who choose to return, while supporting those who need to work remotely or feel more comfortable doing so," he said.

"Our goal is to give employees further flexibility, allowing people to work where they feel most productive and comfortable, while also encouraging employees to work from home as the virus and related variants remain concerning."

At the headquarters in the northwest state of Washington "we've been closely monitoring local health data for months and have determined that the campus can safely accommodate more employees on-site while staying aligned to Washington state capacity limits," DelBene added.

Microsoft will adjust levels of in-person and remote work at each of its locations to factor in health conditions, with various stages of reopening.

A company survey found 54 percent of employees favored a "soft open" which gives people the option to spend a portion of time in the office.