Japan spent a likely record daily amount to prop up the yen last week, leaving economists and investors wondering whether the government could intervene again despite skepticism over the impact of such action.

The Finance Ministry disclosed Friday that it spent ¥2.84 trillion ($19.7 billion) in September to slow the yen’s slide in its first intervention to support the currency since 1998. Private analysts had estimated the intervention at up to ¥3.6 trillion.

The widely held view among market participants and economists is that the intervention only took place on Sept. 22 after the Bank of Japan’s stand-pat decision, though the data cover the whole month. More specific details on daily intervention in September and the currency pairs involved will be announced in early November.