Markit Economics said growth accelerated in March with their purchasing managers' index rising from 54.3 in February to 54.6 in March.
That indicates a slightly faster pace of growth.
The Institute of Supply Management, however, said their PMI slipped from 54.2 in February to 51.3 in March, which indicates manufacturing is still growing, but at a slower pace than the previous month.
Figures above 50 in the PMI indicates growth, while below 50 indicates contraction.
Markit said the index for new factory orders was unchanged from February's 55.4. The ISM estimated new orders at 51.4, a drop from February's 57.8.
Markit left its employment index unchanged at 54.6, while ISM said the employment index showed faster growth in March at 54.2 after a posting of 52.6 in February.
"Manufacturers enjoyed another month of strong output and order book growth in March, finishing off the best quarter for two years. The sector will have provided a firm boost to the economy in the first quarter, with output possibly growing by as much as 2 percent -- roughly 8 percent on an annual basis -- compared to the final quarter of last year," said Markit Chief Economist Chris Williamson.
The ISM, meanwhile, said 14 out of 18 business sectors reported growth in March, with the fastest gains in the wood products industry, followed by furniture production, plastic and rubber products, electrical equipment and appliances.