INDIANAPOLIS (AP) — An Indiana proposal to allow fire stations and other public places to install "baby boxes" so mothers in crisis could anonymously surrender their newborns needs further review and is unlikely to advance this year, a key lawmaker said Tuesday.

Sen. Patricia Miller, whose Senate health committee is scheduled to hear the bill Wednesday, said she expects the bill to be amended to send it to study committees for further evaluation.

"There are a hundred unanswered questions," she said. "The bill didn't take effect for 18 months. Why don't we just back up and get the questions answered first?"

The move comes amid a backlash from advocates of safe haven laws, who have contended it would make it easier to surrender a child without exploring other options and could deprive mothers of needed medical care. At least three safe haven groups from across the country spoke out against the measure and urged Indiana to focus instead on promoting its existing safe haven law.

Dawn Geras, president of the Save the Abandoned Babies Foundation in Chicago, on Tuesday called the plan to table the discussions "a wise decision."

"I understand wanting to do everything humanly possible, but you need to think about unintended consequences and how you're going to save the most," she said.

All 50 states and the District of Columbia have laws that allow women to surrender newborns at places such as fire and police stations or hospitals without fear of prosecution provided the child has not been harmed. Supporters say they want to add the baby box proposal to the law to reach mothers who can't face surrendering a child in person and might otherwise abandon infants in unsafe places.

Baby boxes, known in some countries as baby hatches or angel cradles, originated in medieval times, when convents were equipped with revolving doors known as "foundling wheels." Hundreds of children have been surrendered in modern-day versions in place in Europe and Asia, and the devices are in use in at least one Phoenix hospital.

The boxes proposed in Indiana would be equipped with sensors that would set off alarms when the box is opened and again when a weight is detected inside.

Monica Kelsey, a Woodburn, Indiana, firefighter who has promoted the boxes and worked to develop a prototype, did not immediately return a message seeking comment Tuesday.