Security agents raided 19 businesses on Tuesday who they accuse of funding a plot to overthrow the state.
Footage broadcast on Egyptian television showed police officers raiding the firms in the capital Cairo and the cities of Alexandria and Ismaila.
The interior ministry said the busts were in response to the businesses allegedly funding a plot "intent on overthrowing the state and its institutions" this month.
It claimed 250 million Egyptian pounds ($15 million) was seized in the raids which targeted businesses affiliated with the outlawed Muslim Brotherhood group.
The businesses were part of a plan along with groups "claiming to represent civil political forces" which sought to carry out "violent acts and unrest against the state", the interior ministry said.
At least eight people were arrested, including businessmen, journalists and political figures such as prominent human rights lawyer Zyad el-Elaimy.
His mother Ekram Youssef said he was visiting a friend in Maadi, a Cairo suburb, when he was arrested in the early hours of Tuesday.
"Some people grabbed him so he started shouting to his friend. He eventually cooperated with them once the friend came", she told AFP.
Elaimy played a key role in the movement that unseated autocrat Hosni Mubarak in 2011 and he subsequently served as a lawmaker for a year.
Since the 2013 military overthrow of elected Brotherhood president Mohamed Morsi - who died last week after collapsing in court - President Abdel Fattah al-Sisi's government has grown increasingly intolerant of dissent.
Thousands of Islamists as well as secularists have been jailed following trials that have left the international community dismayed while Egypt says it is countering terrorism.