Lyric Cook and Elizabeth Collins case: Iowa cousins' death details kept confidential by police

(CBS/AP) EVANSDALE, Iowa - Authorities won't be releasing details anytime soon about what caused the deaths of cousins  Elizabeth Collins and Lyric Cook, whose bodies were found last month in a park about 25 miles from their homes in northeast Iowa.

PICTURES: Bodies of missing Iowa cousins identified

Evansdale Police Chief Kent Smock told The Des Moines Register on Wednesday that the causes and other details about the deaths of 8-year-old Elizabeth and 10-year-old Lyric will be kept confidential in order to protect the investigation.

Smock says "the only people that are going to know this information are the people who are responsible."

He says tests on the girls' bodies aren't finished yet.

Elizabeth and Lyric disappeared from Evansdale on July 13, 2012. Their bodies were found on Dec. 5.

Complete coverage of the case of the missing Iowa cousins on Crimesider