The U.S. labor market surprised economists with its strength once again, adding more than 300,000 jobs in March, with a few key sectors continuing to fuel its growth.

Health care and social assistance were the top sector for job gains — a common theme in recent years — adding 81,300 jobs. Government and leisure and hospitality were the next two strongest sectors, and together these top groups accounted for more than 60% of March’s gains.

Within health care, ambulatory services and hospitals combined to add 55,000 jobs, according to the Bureau of Labor Statistics. Local government was another strong sub-group for hiring, growing by 49,000 jobs.

Notably, the leisure and hospitality sector is now back to its pre-pandemic employment level, according to the Bureau of Labor Statistics. Employment in this area, which includes bars and restaurants, fell dramatically in 2020 when many such establishments were closed for health concerns.

The continued rebound of these jobs, along with strong months for sectors like construction, could be a sign that immigration is helping the labor market grow without putting too much upward pressure on wages. The Bureau of Labor Statistics noted that the labor force participation has changed little in the past year despite consistent upside surprises for job gains.

“Last year, half of the growth in the labor force came from net immigration. There were 5.2 million additional jobs last year, thanks to net immigration. It’s been the key to rebalancing the labor market. It’s a huge part of the reason we’ve got the growth that we’ve got and the disinflation that we’ve had,” Stony Brook University professor Stephanie Kelton said Friday on “Squawk Box.”