Ads were posted in chat rooms linked to popular Arabic porn sites
Egyptian police have arrested a senior civil servant and his wife accusing them of swapping sex partners with other couples, local media reports say.
The pair are said to have held at least three "swinger" parties at their home in Cairo, after soliciting other married couples over the internet.
Extra-marital sex is illegal in Egypt, where the constitution says Islamic law is the main source of legislation.
Police say they are looking for others who participated in the sex acts.
The couple, who media reports say have children and used the aliases Magdy and Samira, face up to three years in prison if convicted of facilitating prostitution.
Egyptian media reported that the main suspect - a government employee - set up a website to promote wife swapping and posted ads in chat rooms linked to popular Arabic porn sites.
He and his wife - a school teacher - then interviewed some 44 couples, usually at coffee shops in downtown Cairo, before they swapped partners.
Press reports said the pair turned down over 40 couples because they were not officially married, causing concern that they would not guarantee confidentiality.
It said police also arrested a lawyer at a cafe in the Cairo suburb Giza while he was finalising a swap deal, adding that another swap was set for the weekend with a young man from the Gulf and his wife.
Many of the ads on the website used by the couple are said to contain personal email addresses and phone numbers.
A human rights group, the Egyptian Initiative for Personal Rights, criticised police for snooping on the couples.
"The case raises serious concerns about due process and the privacy rights of those arrested, especially in light of press reports about police interception of defendants' electronic correspondence," spokesman Hossam Bahgat told the AFP news agency.
"We're also of course worried that police seem to be still going after many people based on the intercepted emails of the two main defendants."