Two teenagers will be charged as adults for allegedly coating a playground slide with drain cleaner that severely burned a toddler, the state's attorney said.

The teens, who are both 16 and live in the Essex area, were arrested earlier this week and will be charged with assault, Scott. D. Shellenberger said Thursday.

The new charges come from evidence found at the playground and analyzed by a crime lab, Shellenberger said. He declined to elaborate.

Police said the youths broke into a school storage area in Middle River and found bottles of caustic drain cleaner, which they poured on a slide at the school playground to see whether the plastic would burn. When it did not, they departed, leaving the chemical on the slide, police said.

Payton Potochney, 2, suffered third-degree burns after he went down the slide Saturday. He underwent a skin graft and was in fair condition before another surgical procedure Thursday, Johns Hopkins Hospital officials said.

The youths also face juvenile charges of reckless endangerment and burglary.