"A long-awaited Ministry for Magic report made public today warns against the dangers of underestimating Muggles."
-- excerpt from an article in the Daily Prophet (DP1)
This article in the Prophet outlines the findings of a report by a committee on Muggles, headed by Professor Phoebus Penrose, entitled “A Study into Muggle Suspicions about Magic“. Examples given of magic noticed by Muggles in the article are crop circles, UFOs and the Loch Ness monster (DP1).
Although the date printed on the first Daily Prophet Newsletter (DP1) is 31 July 1998, the timeframe for this event is 1992-1993.
From the Web
Writing by J K Rowling on Pottermore:
Harry Potter Wiki: Muggles