Mada Masr, however, has defied the government pressure and continued to publish groundbreaking investigations, including a report last week that the president’s son, Mahmoud el-Sisi, was being removed from his senior role in the intelligence agencies because of his poor performance.

[Read: Hosni Mubarak, Egyptian leader ousted in Arab Spring, dies at 91.]

The Egyptian authorities have blocked access to the Mada Masr in Egypt for the last two years. But the publication has remained an indispensable source of information for Egyptian activists and intellectuals, who can often reach it via a VPN service, as well as for Western analysts and policymakers. Its Arabic name is a play on words that literally means the scope of Egypt but could also refer to a stone-setting, as though Egypt were a jewel.

The tightening of government pressure on Mada Masr escalated Saturday with the arrest of a senior editor, Shady Zalat, 37, in a dawn raid on his home. After being held at an undisclosed location overnight, Mr. Zalat was released on Sunday evening by the side of a highway, Mada Masr said in a statement.

In the hours before his release, as many as nine armed plainclothes security officers raided the Mada Masr offices. The officers detained the organization’s staff, confiscated their telephones, and interrogated them for three hours. The officers also asked some of the journalists to unlock their smartphones and laptops and searched their devices.

The editor in chief, Lina Attalah, along with the journalists Mohamed Hamama and Rana Mamdouh, were then briefly detained at a nearby police station. Ms. Attalah, 36, founded Mada Masr in 2013, shortly before the military takeover that brought Mr. Sisi to power.