The U.S. arm of the financially insolvent SolarWorld AG sent certified letters over the weekend warning all 800 employees in Hillsboro that there could be a mass layoff or plant closure within 60 days.

The notice comes a week after the German solar company's U.S. subsidiary, SolarWorld Americas, said that it was continuing to operate normally.

Solarworld spokesman Ben Santarris said the company is sticking with that assumption, and continues to work with suppliers and customers to determine what the right size of the company should be going forward. But its future remains uncertain after its corporate parent declared insolvency on May 10, and it is required to notify employees under the federal WARN Act, which mandates a 60 day notice of mass layoffs.

German insolvency is roughly analogous to corporate bankruptcy in the United States.

The company sent certified letters to all of its employees Friday evening and followed up with similar emails Monday.

Though SolarWorld's Hillsboro affiliate is separate from its parent, both are subject to the same competitive forces that triggered its German parent's crisis. And SolarWorld hasn't described the financial relationship between the two organizations in detail, so it's not clear just how the insolvency will affect the U.S. affiliate.

SolarWorld and other U.S. solar manufacturers have been under considerable pressure for years, undercut by cheaper products that they say are being dumped on the American market by China.

SolarWorld employs 800 at its Hillsboro plant, a onetime Japanese computer chip factory built in the 1990s but never opened. SolarWorld spent $440 million to adapt the facility, aided by tax incentives worth more than $80 million, state and local officials said earlier this month.

- Ted Sickinger

tsickinger@oregonian.com

503-221-8505; @tedsickinger