Acting on a judge's order, Egyptian police detained the sons of former president Hosni Mubarak on Saturday along with three others in connection with insider trading charges for which the five are on trial, security officials said.

They said the arrests were ordered by judge Ahmed Aboul-Fetouh before he adjourned the case's hearings until Oct. 20. The Mubarak sons - wealthy businessman Alaa and Mubarak's one-time heir apparent Gamal - were taken to a prison south of Cairo after the hearing, according to the officials, speaking on condition of anonymity because they were not authorized to brief media.

The detention of the two brothers came as something of a surprise given that the trial has been proceeding without incident. It was not immediately clear if their detention has anything to do with a recent warning to Gamal Mubarak by a newspaper editor close to the government to abandon any political ambitions.

The two sons and their father were sentenced to three years in prison following their conviction of embezzling funds set aside for the restoration and maintenance of presidential palaces, using the money to upgrade their private residences. The sons were released in 2015 for time served, while Mubarak walked free last year. The trio paid back to the state the money they embezzled.

The three were first detained in April 2011, two months after a popular uprising forced Mubarak to step down after nearly 30 years in power. After a long trial, Mubarak was acquitted of killing protesters during the 18-day uprising against his autocratic rule.

The ongoing insider trading trial centers on the buying by the two brothers of a large number of shares in a local Egyptian bank that they allegedly knew was to become the target of a takeover by an Arab Gulf investor, a move that was virtually certain to dramatically drive up share prices.