ANKARA, Turkey (AP) – Two more Turks tested positive for the deadly H5N1 strain of bird flu in preliminary tests, the government said Thursday, bringing the total number of human infections to 18.

Both victims were from the stricken southeast, and had been in contact with infected birds, officials said.

A Turkish lab also determined that a third person who died of bird flu last week had the H5N1 strain, the Health Ministry said.

Authorities, meanwhile, stepped up the precautionary slaughter of thousands of birds in an effort to keep the outbreak in check.

The Health Ministry said the two new human cases came from the provinces of Siirt and Sanliurfa, in the mainly Kurdish southeast.

“They all have a story of contact with chickens,” the ministry said in a statement. It said the two patients were hospitalized in stable condition, and that authorities had immediately begun destroying poultry in the areas where the two came from.

Experts also found the virus in a lung of the third victim who died last week, an 11-year-old girl who died in a hospital in the eastern city of Van near the border with Iran, the ministry said.

She was a sister of the other two children, both teenagers, who died of H5N1 infection last week in the first fatalities outside East Asia, where the deadly strain has claimed 76 lives.