Union workers at Northrop Grumman Ship Systems’ Ingalls shipyard went on strike Thursday after twice rejecting contract offers from the defense contractor.

All unions, except for office workers, are now on strike at the shipyard, according to Jim Couch, business agent for the International Brotherhood of Electrical Workers Local 733. Office workers will recognize the picket line, he said.

Pascagoula police said there were six different sites where the workers have set up and that police would provide 24-hour security at these sites. The picket line outside the main gate has been orderly, police said.

The strike halted work at Mississippi’s largest private employer. The shipyard, among other things, builds ships for the Navy.

Northrop Grumman spokesman Bill Glenn did not immediately return phone calls seeking comment.

The strike was sanctioned by both the 1,200-member IBEW and the Pascagoula Metal Trades Council. The council represents 11 unions and 6,200 workers.

Employees at Northrop Grumman plants in Gulfport, New Orleans and Tallulah, La., approved their new labor agreements, Glenn said.

In a statement released Thursday by National Medal Trades Department, President Ron Ault said the strike is the result of the stresses of post-storm life.

“Our members at Ingalls are frustrated and angry. Ever since the Gulf Coast storms two years ago their quality of life has taken a nosedive. Housing is expensive and hard to find. Paying for everyday commodities and services like gasoline and even groceries takes a much bigger bite out of their home pay than two years ago.

“What we are seeing here is something like post-traumatic stress in combat troops. They are fed up with what they see as abandonment and neglect of this region. Our members are the world’s best shipbuilders, living in one of the nation’s most devastated areas. Something has got to give,” Ault said in the statement.

The latest version of the contract offered by the shipyard’s management wouldn’t give workers enough of a raise to offset cost-of-living increases caused by Hurricane Katrina, IBEW members said.

The last strike inside the Ingalls yard was in 1999.