The gold -- 55.51kg to be precise -- stolen from Dhaka Customs House was taken from 437 separate packs kept inside a customs warehouse at Hazrat Shahjalal International Airport.

The thieves didn't take the entire contents from the packs; rather, they pilfered only small portions of gold from the packs before putting those back, according to investigators.

All these gold items were seized under the DM (detention memo) criteria, as these were supposed to be released upon payment of fines and taxes.

To distinguish one item from another, officials placed the DM items in separate packs and sealed them with tape. The gold was pilfered from 437 of those items, which were seized between 2020 and August of this year.

"It is not possible for a common person or a thief to enter such a secure place at the airport. Even then, if anyone enters, they will not take a portion of gold from a pack; they will take the whole batch," said Morshed Alam, deputy commissioner of Uttara Division Police.

"We also found the instruments that were used to break the vault and cut the window," he told The Daily Star.

Police seized a cutter, an axe, and a Chinese knife from the warehouse.

Referring to the available evidence collected so far, he said, "Everything points at the involvement of insiders with access to the warehouse, rather than an outsider."

Investigators said there were no CCTV cameras within the customs warehouse.

Tohidul Islam, additional deputy commissioner of Uttara Division Police, said there was a CCTV camera at the entrance of the customs warehouse.

"But we came to know that the camera was not working on the night of September 1 when the gold was reportedly stolen from the warehouse," he said.

According to the first information report filed on Sunday by Dhaka Customs House with Airport Police Station, the theft took place on September 1.

Meanwhile, police detained the four security guards -- Rezaul Karim, Mozammel Haq, Afzal Hossain, and Niamat Hawlader – of the customs house for interrogation early yesterday.

One of the investigators said Niamat had failed to give satisfactory answers to questions asked about the theft.

"There is a major gap between Niamat's digital movement and statement. So, we are closely investigating his role in the incident," the official said, requesting anonymity.

In another development, police yesterday evening detained the four Assistant Revenue Officers (AROs) -- Shahidul Islam, Saidul Islam Shahed, Akram Sheikh, and Masum Rana -- for interrogation as they were in charge of the warehouse.

ADC Tohidul Islam confirmed the development to this newspaper.

Customs sources said AROs Shahidul and Saidul had been in charge of this warehouse since last November.

On August 1, they were transferred to the cargo unit of Dhaka Customs. After that, AROs Akram and Masud were put in charge of the warehouse.

Upon assuming responsibility, Akram and Masud signed a document stating that the inventory of seized products was consistent and that no items were missing.

But around 13 days later, on August 23, Shahidul and Saidul were transferred back to the same warehouse.

Contacted, Dhaka Customs House Commissioner AKM Nurul Huda Azad said, "Four electronic locks were purchased a month ago for added security of the gold kept at the warehouse on a temporary basis. As Shahidul and Saidul were previously in the same position, they were transferred back to the warehouse."

However, a police high-up, involved with the investigation, said anomalies in the gold inventory were first detected on August 13, after six gold bars went missing from the vault.

Senior customs officials then summoned Shahidul and Saidul, and asked them why the gold bars were missing, said the police official, adding that the gold bars were found inside the warehouse a day later.

Sources said digital footprints between Shahidul and some goldsmiths in the capital's Tanti Bazar area were found.

Dhaka Customs House has formed a nine-member probe committee in connection with the stolen gold.

The committee, headed by Dhaka Customs House Additional Commissioner Kazi Farid Uddin, has been asked to submit a report within seven working days.

Dhaka Customs House Joint Commissioner Minhaj Uddin told The Daily Star that the committee would look into whether there was any negligence in storing the gold.

After this incident at Dhaka Customs House, the Chattogram Customs House is also taking extra precautions. After the HSIA, the highest number of gold seizures in the country takes place at Chattogram Shah Amanat International Airport.

Talking about security of seized items, Chattogram Customs House Commissioner Mohammad Fyzur Rahman said, "All measures have been taken as per the law for the security of the seized gold and jewellery."

Preparing an inventory of all kinds of valuable goods at Chattogram Customs has begun. However, extra precautions have been taken considering the reality and legal constraints, he said.