The index stayed in the green most of the morning but started to dip before the lunch break and closed over seven points lower after rising nearly 15 points Tuesday.
FLC of real estate developer FLC and related speculative stocks like ROS of FLC Faros Construction and AMD of FLC Stone Mining and Investment traded at floor prices after FLC chairman Trinh Van Quyet was arrested for alleged stock manipulation.
Their plunge, however, did not create a ripple effect on the market, as investors still bought the dipping blue chip stocks such as BID of state-owned lender BIDV and HDB of HDBank.
Trading value on the Ho Chi Minh Stock Exchange (HoSE), on which the index is based, surged 22 percent to VND28.68 trillion ($1.24 billion).
The VN30 basket, comprising the 30 largest capped stocks, saw 17 tickers falling, with NVL of real estate developer Novaland Group being the top loser with a 3 percent slip.
PLX of fuel distributor Petrolimex dropped 2.5 percent, and PNJ of Phu Nhuan Jewelry fell 2 percent.
Other losers included GVR of Vietnam Rubber Group, down 1.9 percent, and POW of electricity producer Petrovietnam Power Corporation, down 1.8 percent.
Twelve tickers gained, led by four banks: BID of state-owned lender BIDV, HDB of HDBank, MBB of lender MB and VPB of private lender VPBank, increasing by 1.1-2.7 percent.
Foreign investors were net buyers to the tune of VND123.65 billion, focusing on DGC of Duc Giang Chemicals Group and DXG of real estate developer Dat Xanh Group.
The HNX-Index for stocks on the Hanoi Stock Exchange, home to mid and small caps, plunged 2.17 percent while the UPCoM-Index for the Unlisted Public Companies Market fell 0.42 percent.