Connecticut's top lawyer has issued a warning about at-home rape kits, with prosecutors saying the evidence they collect might be useless.

Attorney General William Tong is launching an investigation of two at-home rape kits that are available online: MeToo and PRESERVE.

"Because it is a very evidence-intensive crime to prove and to prosecute, law enforcement needs to be sure that the evidence that it's collecting is reliable and admissable," he said.

Waterbury State Attorney Maureen Platt says the state has specific guidelines for health care providers when it comes to rape kits.

"For instance, some evidence must be kept in paper bags," she says. "It must be airbagged first. If they're not air dried in a certain way, we can lose that evidence permanently."

The makers of MeToo kits say they are working with states to make sure they meet legal standards. The founder of PRESERVE insists evidence collected by a victim can be admitted in court.

But a Fairfield detective says home kits can miss things.

"It may be something like saliva taken from a certain area of the body, or epithelial cells that are swabbed," said Detective Kerry Dowling. "And the DIY kits, to the best of my knowledge, doesn't offer any of that."

Sexual assault victims can get an official rape test for free at any emergency room, even if they don't press charges. Those kits are tracked and saved, and matched up to a national database.