The facilities at the Bulgarian port Burgas according to a Cia report dated 13 March 1953

An item reported that the harbour of Burgas, Bulgaria was under complete control of the Soviet Union and there was a lot of army personnel visible in contrast to the small number of navy personnel. In Burgas was a naval repair yard available. The personnel consisted of Bulgarian labourers, the board and technicians however were Soviet. On their caps was an anchor interwoven with 2 flags and surmounted by a star visible. There were at least six concrete built warehouses available in the port zone. Two were recently built. Furthermore was the port zone covered by a railroad line/

Source
The report was published on www.archive.org, document number CIA-RPD80-00810A000500330005-5.