Law enforcement sources tell TMZ ... investigators have been following up on the leads ... but so far, no contact has been made with Nick.
TMZ broke the story ... Stahl's wife filed a missing persons report with the LAPD this week, saying she hasn't seen or heard from him since May 9th.
Stahl's wife is concerned the actor has been frequenting Skid Row in Downtown L.A. -- a known drug spot.
TMZ obtained photographs of Nick at a bar in Downtown L.A. on Wednesday May 2nd ... where witnesses tell us he appeared intoxicated ... but no more than your average bar patron.
Sources close to Nick tell TMZ he has reached out to friends via email to tell them he is ok and seeking treatment.