The yen was trading just shy of 150 per dollar levels in late U.S. trading, keeping investors on high alert for possible intervention to support the currency, which some speculate could happen once the yen breaches the 150 level.

Japan’s currency weakened as much as 0.44% to 149.9055 against the dollar Wednesday in a trading session that saw the greenback strengthen as Treasury yields climbed to multiyear highs. The yen is trading at a level last seen 32 years ago and follows a depreciation of more than 22% against the dollar this year, even after Japanese authorities stepped in to stem volatile currency movements in September.

“Don’t be surprised if the BOJ comes in again to intervene over the next few days, not to reverse this move but to simply introduce some two-way risk,” said Win Thin, global head of currency strategy at Brown Brothers Harriman & Co.

The continued yen slide is also fueling anxiety that Japanese authorities are partaking in stealth intervention tactics as investors are observing sudden, short-lived bursts of yen strength as it edged to its fresh low Wednesday.

“We are in a rising USDJPY market, and generally in a rising market the bursts go in the direction of the uptrend,” said Greg Anderson, Bank of Montreal’s global head of FX strategy. “But since the middle of last week, we’ve had a bunch of 15 pip or more moves to the downside. That’s the pattern I would expect to see with stealth intervention.”

Some market observers struck a more cautious tone, chalking the moves up to volatility.

“Markets are horrific right now and session ranges are enormous,” said Daniel Tenengauzer, head of markets strategy with BNY Mellon. But “I’ve been through those kind of interventions and those moves are much larger.”