The regulator did not provide further details in its statement, published on Tuesday.
Last month, Velina said that it has received a buyout offer by Tomov Development, priced at 8.40 levs ($4.74/4.29 euro) per share.
Tomov Development acquired 94.55% interest in Velina through deals in the period September 30 - October 8.
The buyout bid values Velina at some 12.85 million levs.
Velina shares last traded on the Bulgarian Stock Exchange at a price of 8.35 levs.
(1 euro = 1.95583 levs)