Investor money gushed into stock-based funds during the first full week of trading in 2018, another potential trigger sign of an overheated market.

"The bull capitulation begins," Michael Hartnett, chief investment strategist at Bank of America, said in his weekly fund flow roundup.

The numbers were stunning for a week during which stocks added around 1 percent to the already eye-popping gains that began shortly before the November 2016 presidential election.

Stock funds raked in $24.4 billion for the week through Wednesday, a total that Hartnett called "blockbuster" and was spread across the equity spectrum. It was the sixth-biggest equity inflow total ever and the most in at least six months.

The total was diverse geographically — $6.4 billion to the US, with $3.2 billion to Japan, $2.2 billion to Europe and $4.3 billion to emerging markets, the largest inflows for that group in 73 weeks. There also was some dispersion between active and passive strategies.

Exchange-traded funds, a mostly passive group that tracks market indexes like the , have been attracting the bulk of investor cash during the nearly nine-year bull market run, while active funds have seen continuous outflows. However, active mutual funds garnered $2.1 billion of the weekly inflows to start the year.

"Investors are unambiguously long and will likely stay so until rates go up and/or [earnings per share] goes down," Hartnett said.

There was plenty of cash to go around, even outside stocks.