The National Investigation Agency probing the gold smuggling case in Kerala on Thursday questioned suspended senior IAS officer M Sivasankar for nine hours, two months after he was quizzed by the agency twice in connection with the sensational case, sources said.

Sivasankar, who appeared before the NIA team here at 11 am, was reportedly quizzed in the presence of Swapna Suresh, a key accused arrested by the NIA in the case.

He was let off at around 8.15 pm, sources said.

The former principal secretary to Chief Minister Pinarayi Vijayan was questioned a day ahead of the four-day NIA custody period of Suresh ending.

This is the third time the officer appeared before the agency after allegations of his link with Suresh in the case surfaced.

Sivasankar was questioned twice earlier in July --at Thiruvananthapuram and at the NIA Kochi office.

He was again summoned for questioning as the NIA intensified its investigation on the basis of digital evidence is obtained from the arrested accused including Suresh.

The NIA, which earlier once interrogated Suresh, had informed the court that further custodial interrogation of the accused would be required on the basis of the digital evidence to be obtained.

The agency had said the accused needed to be confronted with materials found in the digital devices by taking them into further NIA custody.

Action was taken against Sivasankar after allegations surfaced that he had links with Suresh, the key accused in the case related to the attempt to smuggle gold through diplomatic baggage using the name of an official in the United Arab Emirates (UAE) consulate in Thiruvananthapuram.

The Customs seized the gold, weighing over 30 kg and valued at around Rs 15 crore on July 5.

The NIA has booked several people, including Suresh, Sarith P S, Sandeep Nair and Faizal Fareed, under the Unlawful Activities (Prevention) Act.

Suresh and Sarith are former employees of the UAE Consulate and allegedly used their past connections to smuggle gold using the diplomatic channel.