It looks as if the spring swoon is back.

American employers added an estimated 88,000 jobs to their payrolls last month, compared with 268,000 in February, according to a Labor Department report released Friday. It was the slowest pace of growth since last June, and less than half of what economists had expected.

It also was the start of a third consecutive spring in which employers tapered off their hiring after a healthy start to the year. Slowdowns in the previous two years could be attributed to flare-ups in the European debt crisis, but this time the cause is less obvious. The recent payroll tax increase or other fiscal tightening in Washington could be partly to blame for the sudden retreat in hiring, but neither seems to be showing up much yet in other relevant economic data.

“People were starting to believe the economy was really picking up steam, and desperately wanted this report to be better,” said Joshua Shapiro, chief economist at MFR Inc. “But that didn’t happen.”

Economists like Mr. Shapiro cautioned that the numbers, which are adjusted for normal seasonal variations, are volatile from month to month and are still subject to revision.