A large police operation kicked off at a reservoir in Portugal on Tuesday after police investigating the disappearance of Madeleine McCann say they received “certain tip-offs.” Divers were seen entering the waters at the Arade dam on Tuesday morning around 31 miles from where the British toddler vanished 16 years ago. German prosecutor Christian Wolter said he could not disclose information about the tips received by police or what officers are hoping to find at the reservoir, where some investigators were spotted searching the woodlands surrounding the water. German authorities previously named Christian Brueckner as the main suspect in the case. He is currently serving prison time for the rape of a 72-year-old American woman.