The $1 billion state-owned Forestry Corporation is facing half a dozen separate investigations into its timber logging operations around the state.

The investigations, which include scrutinising thousands of alleged breaches of environmental controls at Cherry Tree State Forest in the north of the state come after the Forestry Corporation has been hit with 46 fines during the past five years for offences including breaching threatened species regulations, polluting waters, not marking trees or exclusion zones and not properly searching for koala habitats.

The Forestry Corp, which has assets of $1.2 billion and in the past financial year reported profits of $52 million before tax with a $19 million dividend paid to NSW Treasury, was also issued with six clean-up notices during the same period.

The highest fine issued to Forestry Corporation by the Environment Protection Authority was $15,000 last month for a major erosion incident in Tuckers Nob Forest near Coffs Harbour.