The worst week of outflows in six years for a Treasury-focused ETF can be traced back to two huge trades.

BlackRock Inc.’s $16.2 billion iShares 7-10 Year Treasury Bond exchange-traded fund (ticker IEF) saw a combined 12.4 million shares hit the tape 4:10 p.m. in New York on Friday, according to data compiled by Bloomberg. While it’s unclear if the two block trades -- worth $723 million and $775 million -- were to buy or sell IEF, they line up with the fund’s nearly $1.4 billion outflow. For the week, investors pulled $2.2 billion from IEF, the most since 2014.

JPMorgan Chase & Co and FMR LLC were the only holders big enough to make two trades of that size, the latest available data showed. The massive trades could be related to a rotation from Treasury funds into corporate-bond products after several coronavirus-vaccine breakthroughs fueled a rally in riskier assets. Credit funds pulled in $4.6 billion last week, while government-bond ETFs posted $2.6 billion of outflows.

“IEF is very popular with the models and even big institutions,” said Eric Balchunas, an ETF analyst at Bloomberg Intelligence. “If anything, it could be model signals are getting triggered because corporates have separated from Treasuries this month.”

The $41.2 billion Vanguard Intermediate-Term Corporate Bond ETF (ticker VCIT) has climbed 1.3% in November. IEF has risen only 0.2%.