Shares in Overhill Farms Inc. gained more than 4 percent Thursday as the company announced an aggressive expansion and upgrade plan for its Vernon manufacturing facility.

The private-label frozen foods maker said it is investing $7 million toward improving the plant’s manufacturing capacity; with a new production line and pasta-making equipment, as well as upgraded freezers, packaging machines and other equipment.

The company said it estimates the upgrades will add almost $100 million to annual sales. Overhill had revenues of $168 million in 2006.

Shares in Overhill rose 24 cents to $6.01 in afternoon trading Thursday on the American Stock Exchange.