MILAN, May 27 (Reuters) - Italy's antitrust authority said on Wednesday it had opened an investigation into drug maker Biogen Italia and its parent Biogen BIIB.O over alleged abuse of dominant position.

The two companies allegedly aimed at excluding rival Sandoz SDZ.S from offering multiple sclerosis drugs, based on active ingredient natalizumab, the regulator said in a statement.

The watchdog carried out inspections at Biogen's Italian offices, assisted by Italy's finance police, it added.

Biogen was not immediately available for comment.