The National Investigation Agency (NIA) on Saturday took the main accused in the gold smuggling case in Kerala to capital Thiruvananthapuram for evidence collection.

On Saturday morning, NIA first raided key accused Swapna Suresh's house in Thiruvananthapuram and later in the afternoon, investigation officials took one of the other accused -- Sandeep Nair, to an apartment that the accused had rented out in a building called 'Heathers' near the Kerala Secretariat.

Officials believe that it is in this apartment, which was rented out for a few days in May, that the conspiracy for gold smuggling was planned.

According to reports, though Sandeep Nair was taken near the building, he was made to sit outside in a car while officials went inside. Meanwhile, another batch of NIA officials are believed to have taken Swapna to other places to collect evidence.

In its custody application to a special court in Ernakulam, the NIA had said that, "Each of the evidence collected needs to be confronted to the accused and existence of further evidence needs to be probed and then collected without which prosecution would be put to heavy loss."

According to sources, NIA plans to take the other accused, including Sarith, to various places and may also conduct a joint questioning session.

Meanwhile, reports also suggest that bureaucrat M Sivasankar may be questioned again in connection with the apartment that was rented out in the 'Heathers' building.

Already, technocrat Arun Balachandran who was a 'IT fellow' of the Kerala Chief Minister, had said that he had called the 'Heaters' building to rent out an apartment to Swapna Suresh at the behest of Sivasankar.

The case pertains to the seizure of 30 kg of gold from at the Thiruvananthapuram airport, in a supposed consular bag, that arrived from UAE.

On Friday, the Customs Department in the state had reported the arrest of two more people in the sensational case. With this, 11 people have been arrested in connection to the case so far.