NEW YORK (AP) — Some of the world’s wildest action in financial markets is roiling around the Japanese yen.

The value of Japan’s currency has tumbled so much that for a moment on Monday it took 160 yen to equal $1. A few years ago, it took closer to 100 yen to make a U.S. dollar. The yen has been so weak that it’s back to where it was in 1990, shortly after Japan’s famous “bubble economy” burst.

After it briefly touched the 160 yen level in overnight hours for traders in New York, the value of a dollar quickly shifted back to 156 yen by midday Monday on the East Coast. Such sudden moves can happen in the foreign-exchange market, which can be notoriously volatile. Trading may also have been jumpy because of a holiday in Japan that kept its stock market closed. But the speed and degree of the yen’s swings raised speculation about whether Japanese officials were making moves to prop up the value of their currency.