Officials threaten those who refuse with criminal investigations.

TULSA, Oklahoma - August 21, 2008 - Oklahoma police investigating the shooting deaths of two girls have told area residents with guns to bring them in for a test to determine whether they were used in the attack, sparking concern among those who own guns for hunting and self-defense.

According to reports in the Tulsa World the Oklahoma State Bureau of Investigation sent letters to members of the community who were registered as owning .40-caliber handguns suggesting they voluntarily bring in their gun or guns for a test.

The individuals who were "invited" to bring their guns in but didn't now will be included in the ongoing investigation, as well as people who were identified by former owners as having purchased that type of weapon recently, authorities said.

"We'll be checking on them," Jessica Brown, a spokeswoman for the Oklahoma State Bureau of Investigation, told the newspaper.

The investigation is into the June 8 shooting deaths of Skyla Jade Whitaker, 11, and Taylor Paschal-Placker, 13, who died when they were shot several times on a road about four miles from Weleetka. Authorities say two guns were used in the killings, but they haven't released much information about the weapons until they now confirmed one was a .40-caliber.

They have not yet identified the second type of weapon used.

Authorities said they sent out about 60 letters, and about 40 gun owners voluntarily brought in their weapons to the Okfuskee County Courthouse at Okemah for testing over the weekend.

Brown said those weapons were taken by investigators and test-fired, and the results of those tests now are being evaluated. She said nearly half a dozen former gun owners contacted authorities to identify new owners, and another 15 gun owners did not show up.

Those who participated in a forum on the newspaper website expressed sympathy for the victims and their families, but worried about the maneuver of inspecting privately owned guns without a search warrant or probable cause.