Morium's mother Maya Begum filed a case accusing five people, including Younus Mia and his wife Sonia Akhter, 30.
Police arrested Yunus Mia on Saturday.
Maya Begum wailed, "I fed my daughter on Thursday, the day she was killed, at madrasa. At around 2:00pm, madrasa director Jamal Uddin informed me that Morium fell ill. Without informing me, they, Jamal and Yunus, hospitalised my daughter at around 3:00pm. Later, I went to the hospital and learned that Morium is no more. Yunus and his wife killed my daughter. I want justice."
"Yunus and Sonia killed my daughter. Habiba Akhter, wife of Jamal Uddin, helped them cover up the murder. Therefore, she has been made an accused in the case. I came to know it later that Jamal is also involved in the murder. I am trying to make him an accused in the case too," Maya claimed.
Prothom Alo couldn't reach Jamal Uddin for comment as his phone was switched off.
Meanwhile, emergency unit physician of Munshiganj general hospital Mohammad Toffazzel Hossain said Morium was brought dead. Later, the body was sent to the morgue for autopsy.
Officer-in-charge (OC) of Munshiganj Sadar police station Tariquzzaman said the body bore injury marks on the neck. The main accused Yunus Mia has been arrested. The drive is underway to arrest the remaining accused, he added.