The 61-year-old Congress leader was at the Crime Branch office in the evening for an hour.
The veteran Goa politician was questioned for the first time last week after police arrested Anand Wachasunder, a senior official associated with a water augmentation and sewerage project, funded by Japan International Cooperation Agency (JICA), that is at the centre of the scandal involving Louis Berger, a US-based management consultancy firm.
"I am cooperating with the police. I have responded to all their queries," Kamat told PTI after emerging from the Crime Branch office.
Kamat was heading the Congress-led government in 2007-2012 when the US firm allegedly paid bribes to get consultancy contract for the project.
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Former Public Works Department Minister Churchill Alemao was also grilled by Crime Branch in connection with the case last week. Tenders for the project were floated by PWD.
The bribery scam of USD 9,76,630 for the project included kickbacks allegedly paid by New Jersey-based Louis Berger to a then Goa Minister.
Earlier in the day, former Louis Berger Vice-President Satyakam Mohanty was arrested in connection with the pay-off scandal.