SOFIA, Oct. 11 (Xinhua) -- The Bulgarian authorities have seized ancient gold treasure and arrested a four-member organized criminal group responsible for illegal trade in artifacts of cultural and historical value, officials said here on Thursday.

One of the group members was an officer from the State Agency for National Security and arrested while trying to sell an ancient gold wreath in Simeonovgrad on Monday, Deputy Prosecutor General Ivan Geshev said at a press conference.

Three potential buyers of the wreath were initially arrested but then released, Geshev said.

Later on, the authorities also seized a gold necklace weighing almost one kilogram and two gold bracelets of about 250 grams each, which were a part of this treasure.

Hristo Popov, vice director of the National Archaeological Institute with Museum at the Bulgarian Academy of Sciences, said the artifacts were dated to the second half of the 4th century BC. They were of high cultural and historical value.

The investigation is ongoing.