Chinese investors chasing gains in Japan stocks have caused a spike in the premium on an onshore exchange-traded fund tracking the market, triggering a warning from the fund’s manager and a temporary trading halt.

The premium on China AMC Nomura Nikkei 225 ETF’s shares over their underlying net assets surged to as much as 23% before settling at 9.5% on Tuesday. The ETF closed 4.3% lower. Trading in the fund will be suspended until 10:30 a.m. local time Wednesday, the issuer said in a statement.