If others from your college have got offers, you too should get it soon. Usually they release offer letter only when your date of joining is finalised, and they do it close to the date of joining. Also, they try to mix people from various parts of the country.
What you can do:-
(1) Write to their freshers onboarding specific email id, or you can even drop them a message over linkedin (but just one polite message, don’t bug). You can also take the HR’s email from your friends who have got the offer letters, those specific HRs may have some idea. Keep in mind though, that HRs usually don’t reply unless they have some definitive answer to your question.
(2) Keep searching for other opportunities too