DES MOINES, Iowa (AP) _ A state of emergency was declared Friday by Iowa Gov. Terry Branstad with nearly 17 million chickens and turkeys dead, dying or scheduled to be euthanized due to a widening bird flu outbreak.

The proclamation, in effect until May 31 unless terminated earlier, activates disaster response and recovery procedures for the state’s homeland security and emergency management personnel. It also authorizes use of state resources, supplies, equipment and materials to track and monitor bird flu, establish restrictions around affected farms and assist in the rapid detection of cases.

It also allows state agencies to help in the disposal of poultry carcasses, an increasing problem in a state where about 27 percent of its 60 million egg-laying chickens will be wiped out.

Iowa is the nation’s leading egg producer, providing one of every five eggs consumed in the country. The state is ninth in turkey production and has lost well over 110,000 turkeys. The state now has 21 cases of the H5N2 virus in 10 counties.

Overall, the outbreak has led to Midwest chicken and turkey producers losing more than 21 million birds. Minnesota, which has lost some 4 million birds in 19 counties this spring, declared a state of emergency earlier this week.

Four additional farms were added Friday to the Iowa list of those with probable disease outbreak, including a second turkey farm in Sac County and turkey farms in Pocahontas and Cherokee counties.

Madison County, located southwest of Des Moines, is the only county affected that isn’t in northwest Iowa. An egg-laying chicken farm with 1 million birds had a positive preliminary test.

Iowa Secretary of Agriculture Bill Northey said it’s important to step up the state’s response now.

State officials have developed expanded biosecurity guidelines that ask poultry farmers to treat all commercial chicken and turkey farms as potential positive sites and implement strict controls on traffic, personnel and feed.

Northey directed farms to disinfect all vehicles and consider any person on site “something that needs disinfected so as not to spread the virus within the site.”

Authorities have asked producers not to give chickens or turkeys kept in largely enclosed barns feed that is stored outside. Spilled feed should be cleaned up to avoid attracting wild birds, which researchers have suggested first dropped the virus on the farms during migration.

He said as biosecurity is increased and weather turns warmer, officials hope the virus will die off.