Calcutta, Nov. 15: A huge quantity of narcotics seized from the port area last night had landed from Hong Kong early last month after passing through several ports in Southeast Asia.

According to officials of the Narcotics Control Bureau, which conducted the raid, the drugs packed in a sealed container had been lying in the port area since October 4, the day it reached Calcutta. The NCB said the substance was in liquid form, but other details are not known.

“We will send it to the Central Forensic Science Laboratory to find out the exact composition of the seized substance, which seems to be valued at around Rs 50 crore. The character of the liquid can only be revealed after the report from CFSL reaches us,” said an official.

Around 9.30 pm yesterday, a team of 50 from the NCB swooped on a godown of a construction company on Transport Depot Road. The officers sealed all the entry and exit points before starting their search. They did not allow workers and labourers to leave or enter the site during the raid, which ended around 3.30 am on Wednesday.

“During the course of the raid, we found a sealed container with a tag suggesting electronic goods were kept inside. We opened it and found the liquid substance,” said another official.

“There were no valid papers. We picked up seven persons and detained them for interrogation,” he added.

The CID will soon send a team to the narcotics bureau to get details about the seizure. “After, that we will hold a probe separately,” said an officer.

NCB officials — both here and in Delhi — are tightlipped about the case. “Right now, we can not reveal anything regarding the seizure because multiple agencies from different countries are probing into it. We are busy today assessing the seizure and completing the process for sending the substances to CFSL. An official briefing from NCB will be held only after November 23,” said an officer from Delhi.

According to preliminary investigations, the consignment travelled through Bangkok and Thailand before making its way to Calcutta. Narcotics agencies in China and other countries through which the substance was sent are conducting independent probes.