Circle inspector Chaitanya Krishna said the accused Allaka Srinivas, his wife Kameswari, and brother-in-law Andra Sandeep needed money to pay off debts, and therefore planned to kidnap the girl.
They abducted the girl who lived in the same neighbourhood as them on Monday and called her grandfather Shonti Nageswarao demanding a ransom of Rs 4 lakh.
However, fearing arrest, they released the girl on the outskirts of the city a couple of hours later.
Police identified the trio from CCTV footage and arrested them today.