The standard NH Property Disclosure has the following question: "Do you have knowledge of methamphetamine production ever occurring on the property (Per RSA 477:4-g)?" You get to answer Yes or No. There are ways you can parse that question, but you have to ask yourself, would a judge consider that you knew about it or not?
I listed a property a while ago that was busted as a meth lab and sat vacant for several years thereafter, but the owner said he never had any proof that they actually found meth there, just that it was busted. I checked with the city Environmental Protection Division, Planning Department, and Fire Department, and they all disclaimed any jurisdiction over the matter and none of them had any idea what department in the city government would track it.
If there was in fact a meth lab, I think the only entity that would have a record would be the state Department of Environmental Services, but they don't track whether it was cleaned up. If you DM me I can give you a contact person there you might check with, as well as two companies who can test for it (a few thousand dollars just to test) since most local environmental companies (Peniel, Envirovantage, etc.) won't.
In my case, the building was infamous in the neighborhood and everyone referred to it as "the meth lab," so even though the owner would not answer "Yes" to that Disclosure question, I told everyone who looked at the building that there was a stong likelihood that there had been a meth lab there. Surprisingly, not a single person who looked at the building cared. Sold it with no problem.