Malik Ahmed Khan, a spokesperson for the Punjab government, told Arab News that the suspect was arrested in the central Punjab district of Pakpattan.
“We have found some initial evidence and we have reason to believe that he is the one we were looking for,” Khan said.
He added that it was a difficult job to track down the suspect because he had moved around a lot and disguised his appearance.
“He modified his look,” Khan told Arab News. “Sometimes he wore glasses, other times he shaved his beard.”
Zainab went missing in her hometown of Kasur on January 4. Her body was found in a rubbish dump on January 9.
Khan said further details about the suspect would be available once forensic tests were completed; adding that other suspects had been released after DNA tests cleared them of any involvement in the child’s murder.
The suspect has been named in various media outlets as Imran Ali, and he had reportedly been arrested earlier in the investigation, but was released after Zainab’s family said he was a “trusted” acquaintance.
“His appearance is similar to that of the person last seen with Zainab in CCTV footage,” a senior police officer in Lahore told Arab News.
Zainab’s murder caused a huge public outcry in Pakistan. She was reportedly the 12th child to have been murdered in the last year in, or around, Kasur.
The Punjab government formed a joint investigation team that interviewed around 1,100 people, many of whom had their DNA tested.
Punjab Chief Minister Shehbaz Sharif also offered a reward of 10 million rupees for anyone who provided information about Zainab’s killer.
Sharif was expected to formally announce Ali’s arrest on Tuesday.