The Port of Long Beach posted a 17 percent increase in cargo volume in May, its highest level in nearly three years.

More than 580,000 containers moved through the port in May, according to figures released Monday. Imports increased 22 percent compared with the same month last year. Exports were up by 14 percent in the same period. The transport of empty containers from Long Beach , which are sent overseas to be refilled with goods, was up 10 percent over the year earlier.

The port attributed the increase partly to relocation of operations by CMA CGM and Mediterranean Shipping Co., which left the Post of Los Angeles last year. The shift in business resulted in a nearly 13 percent drop in volume in May at the Los Angeles Port compared to the year earlier.

More than 480,000 containers moved through the port of Los Angeles in May, the Los Angeles Port reported on Friday, with imports down 12 percent compared with the same month last year and exports dropping 16 percent in the same period.

Import volume at the Port of Long Beach in May reached its highest level since August 2010, while export volume was the highest since October 2010. Cargo container volume through the first five months of 2013 was up 17 percent over the same period last year.