Fremont tech firm Bitmicro Networks Inc. has agreed to pay about $161,268 in back wages to engineers from the Philippines after illegally paying them below the minimum wage.

The agreement, detailed in a document filed Tuesday with the U.S. District Court for the Northern District of California, was the result of a federal Department of Labor investigation that found Bitmicro had been paying some workers $1.66 an hour. The legal federal minimum wage is $7.25 an hour. (California’s minimum wage is higher.)

The 18 affected workers came from Bitmicro’s subsidiary in the Philippines. They were brought to Fremont from July 21, 2012 to July 20, 2015 under B-1 visas, typically used to bring international workers for training or conferences.

But while those workers were in the United States, they were paid in Philippine pesos instead of dollars, and their pay was not adjusted to U.S. wages. Some workers did not receive overtime, even though they worked an average of 57 hours a week, the Department of Labor said. While the workers were in the United States, Bitmicro put them up in a hotel, said Michael Eastwood, an assistant district director at the Labor Department’s Wage and Hour Division.

Bitmicro, which manufactures flash storage systems, also illegally shipped goods created by these workers while they were not earning minimum wage in the U.S., according to the Labor Department. The company did not respond to the Chronicle’s request for comment Tuesday.

Bitmicro claimed that the wage issue was an oversight, Eastwood said. But he added that the department has seen other cases like this, where international workers at tech firms aren’t being paid fairly.

“We have reason to believe this is unfortunately widespread, with tech companies taking advantage of the system and vulnerability, with overseas workers not likely to complain about the situation,” Eastwood said.

Some companies that have failed to pay workers adequately in recent years include Fremont’s Electronics for Imaging and Bloom Energy Corp. in Sunnyvale. Both firms were ordered to pay back wages to the workers. Electronics for Imaging in 2013 paid some technicians from India as low as $1.21 an hour in rupees, while Bloom Energy was ordered to pay back wages to 14 Mexican workers who had earned $2.66 an hour in Mexican pesos.

In addition to back pay, Bitmicro will also pay penalties of $7,920.

Wendy Lee is a San Francisco Chronicle staff writer. Email: wlee@sfchronicle.com Twitter: @thewendylee