Your options are going to depend on what is in your lease. Some leases address illegal activity, and others do not. If they are not in breach of the lease, they you probably can't evict them before the lease is over. On a situation such as you described, unless you have a good bit of experience in evicting tenants, you probably need to get an attorney involved. You not only have concerns about what rights your lease gives you, but you have to be careful of accusing the tenants of illegal activity if they haven't been charged and/or convicted.
This answer is for general purposes only, and it does not create an attorney-client relationship.
(If your lease does not address illegal activity on the property, you need to have a proper lease drafted for the next tenant.) If the tenants are in breach of the lease, you must send them written demand for possession of the property by a certain date and explain the infraction. Then, if they have not left as of that date, you can file a dispossessory action (eviction) in the local court.