From Longman Dictionary of Contemporary Englishbe on the track of somebody/somethingbe on the track of somebody/somethingLOOK FORto hunt or search for someone or something Police are on the track of the bank robbers. → track
Examples from the Corpus
be on the track of somebody/something• Police are on the track of a gang that has robbed five mini-marts in the last month.• Were they really placed as milestones or could we be on the track of the elusive mark stones of great antiquity? 