As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ASH 2610 FROM CLT TO CLE RETURNED TO THE FIELD DUE TO A LAV SMOKE WARNING MSG AND VISIBLE SMOKE IN THE FLIGHT DECK. MAINTENANCE PLACED THE APU BLEED SYSTEM ON MEL AND THE A/C DEPARTED WITHOUT FURTHER INCIDENT. MAINTENANCE FOUND THE APU OIL CAP OFF, SECURED CAP AND OPS CHECKED GOOD.