SEATTLE • Three of the biggest banks in the United States boosted their combined workforce in the first quarter by the most in almost seven years, as JPMorgan Chase and Wells Fargo added 4,200 employees and Citigroup stopped cutting staff.

The growth spurt - revealed as the trio reported earnings last Friday - was their biggest since the third quarter of 2011, according to data compiled by Bloomberg.

It followed an overhaul of the US tax system that benefited banks more than many other industries. The three banks now employ more than 728,000 people.

The hiring is a sign that tax cuts may ease some of the longstanding pressure on US financial firms to whittle costs to shore up profitability. Still, the picture becomes more nuanced when looking at the three banks individually.

Wells Fargo, which accounted for most of the hiring, said last Friday that it plans to shut 300 branches this year - up from the 250 closures that the San Francisco-based bank previously targeted.

At JPMorgan, which added the rest, chief executive officer Jamie Dimon began predicting long before the tax cuts passed that his firm's headcount would grow for years to come. He has said more recently that the tax cuts will help.

And Citigroup contributed mostly by doing nothing. It has reduced its workforce - sometimes by selling units - in all but a few quarters since 2011. It took a rare break as this year began.

Three other big US banks - Bank of America, Goldman Sachs Group and Morgan Stanley - are set to report their quarterly results and headcounts soon.

BLOOMBERG