(CNN) Three schoolgirls who were detained in Burundi for doodling on a picture of the President have been expelled from school following their release from jail, Human Rights Watch told CNN.

The girls, who are all minors, were detained for six days last month at Ngozi Central Prison and charged with "insulting the head of state," President Pierre Nkurunziza, according to the rights agency.

Their detention sparked worldwide anger with many taking to social media to post defaced pictures of Nkurunziza with the hashtag #FreeOurGirls.

Burundi has freed schoolgirls detained for doodling on President Pierre Nkurunziza's picture in textbooks. It wasn't surprising that the 7 girls were arrested. The big puzzle is what Nkurunziza's pictures are doing in textbooks. What are they teaching in Burundi? #FreeOurGirls pic.twitter.com/VUcm4Z8zC7 — Charles Onyango-Obbo (@cobbo3) March 27, 2019

A boy, who was not charged with any offenses but was arrested as part of the initial group of seven, and another girl were also expelled, HRW's Central Africa director Lewis Mudge told CNN.

"It's good news they were released, but the charges still haven't been dropped, and they have now been expelled from school," Mudge said.