Police said they had arrested a 39-year-old unemployed man on suspicion of murder.
The US urged authorities to release those who were "unjustly detained".
"Hong Kongers will continue to sing. Hong Kongers will continue to hang in there."
Human rights groups, including Amnesty International, have criticised the sentence.
The popular tabloid was forced to fold following a raid by several hundred police.
It was raided by police last year and some staff were arrested.
The parking spot market is fast becoming popular amongst property investors
The vigil is held for the pro-democracy demonstrators killed by Chinese troops in Beijing.
Hong Kong's security chief sent letters to Jimmy Lai and branches of HSBC and Citibank in May threatening jail time.
