ANKARA (AA) – Billionaire Elon Musk told the staff at Twitter on Thursday that remote work is ending in his first email to employees after buying the social media company for $44 billion late last month.

He told employees that they are expected to be present in the office for a minimum of 40 hours per week and he would only approve remote work based on a case-by-case basis.

Musk told the staff to prepare for “difficult times ahead” amid an economic slowdown. He said there was “no way to sugarcoat the message” about challenges.

“The road ahead is arduous and will require intense work to succeed,” Musk wrote in the email that appeared on various news outlets.

He also stressed that the top priority is finding and suspending bots, trolls and spam — an issue Musk strongly raised before buying Twitter.

The moves come after Musk announced last week that half of Twitter’s workforce was being laid off, arguing that the firm is losing $4 million every day.

The Tesla owner and CEO also told executive staff in June at the electric carmaker that remote work was no longer acceptable.