Tenant issues w/ 2 sepearate suites in one house

[Sol Bergren]

Hi, I've been renting a house with a separate entrance basement suite for a few years without too many problems. Recently the upstairs renters contacted us complaining about loud sexual noises and aggressive fighting from the downstairs suite.

The upstairs renters have been renters for over a year now with no problems, the downstairs tenants about 6 months.

We contacted the downstairs tenants and they said they would make a point to keep the noises down. Now a few weeks later the family upstairs has contacted us again with the same complaint. Again we contacted the downstairs tenants, this time in writing on top of speaking with them, basically saying this is the last warning and eviction will be our next action. This has apparently made the tenants downstairs angry, they are claiming their noise levels have been reasonable. Now the downstairs tenants are starting to contact us regarding noise from upstairs and a bunch of small petty complaints. It seems to have deteriorated into a pissing match with us stuck in the middle. We are unsure on how to proceed, especially as this is our first real problems with either of these tenants.

Anyone had a similar situiation? Or suggestions on how to best proceed? Thx!