Perak police chief Datuk Seri Mohd Yusri Hassan Basri said the individuals interviewed included close family members and neighbours of the Teluk Intan Member of Parliament.
"We have also checked the CCTV recordings in the West Coast Expressway area and petrol stations near his (Nga's) family house.
"Investigations are continuing and anyone with information should come forward to help police wrap up our probe," he told a press conference after attending the state-level 217th Police Day celebration here today.
Several pieces of paper with a threatening message directed at Nga were found in front of his mother's house in Ayer Tawar, Manjung, near here on March 7.
On another matter, Mohd Yusri said police had received 443 applications for selling fireworks and firecrackers during the Hari Raya Aidilfitri period this year.
Of this number, 217 applications have been approved, one has been rejected and the rest are still under consideration, he added.
-- BERNAMA
