It can mean either, depending on context.
Afrikaans often uses the simple present form where English may use either:
So Ek werk aan die verslag can mean:
In real usage, context usually makes it clear which meaning is intended.
Because in Afrikaans, werk often takes the preposition aan when you mean working on a project, task, or object.
Compare:
So the thing being worked on is introduced by aan. This is just the normal pattern learners need to remember.
In a normal yes/no question, Afrikaans usually puts the verb first:
Werk ek aan die verslag?
= Am I working on the report? / Do I work on the report?
So the word order changes from:
This verb-first pattern is very common in Afrikaans questions.