Shaimaa Ahmed, a 25-year-old known professionally as Shyma, was arrested by Egyptian police on Saturday on suspicion of "inciting debauchery".
It came after the racy video for her song, I Have Issues, sparked outrage in the socially conservative country.
She has apologised to people who took the video "in an inappropriate way".
"I didn't imagine all this would happen and that I would be subjected to such a strong attack from everyone," she wrote on her now-deleted Facebook page.
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In the video, the singer appears in a classroom with several young men.
Standing in front of a blackboard bearing the phrase "Class #69", she proceeds to eat an apple, banana and some crisps in a sexually suggestive manner.
The scene is interspersed with pictures of her wearing lingerie.
"Shyma presents a lesson in depravity to youths," wrote the Youm al-Sabaa newspaper after the video was released.
On Monday, two days after her arrest, the public prosecutor's office ordered that Shyma's detention be extended for a week, Youm al-Sabaa reported. Arrest warrants were also issued for the directors of the video, it said.
Last year, Egyptian courts sentenced three female dancers to six months each in prison after convicting them of inciting debauchery in music videos.
Another singer is meanwhile facing trial for "spreading provocative publicity" because she suggested that drinking from the River Nile could make someone ill.
A lawsuit was filed after video emerged showing Sherine Abdel Wahab being asked at a concert last year to sing Mashrebtesh Men Nilha (Have You Drunk From The Nile?). She responded by saying "drinking from the Nile will get me schistosomiasis" - a disease commonly known as bilharzia.