PITTSBURGH — A 7-month-old girl was burned by drain cleaner that soaked her diaper while she was at a Pittsburgh-area day care, and state welfare officials were investigating.

Personal injury attorney Martin Lazzaro represents Kimberly Spriggs and her daughter, Brielle, who was burned Dec. 30 at the Butterfly Garden Early Learning Center in McKees Rocks. Lazzaro said Tuesday he’s not sure how the diaper became soaked with the substance, but said the girl was burned on her abdomen, legs and buttocks and will have skin graft surgery Wednesday.

“To the best of my information, there was some liquid Drano brought into the day care center by someone who was an employee that somehow or another ended up saturating the diaper,” Lazzaro told The Associated Press. “She sat in it for roughly two hours.”

Lazzaro said the girl’s mother received a call from the facility that the child had been burned.

The day care is run by Focus on Renewal, a 42-year-old nonprofit that also provides other community services, including a credit union, in McKees Rocks, one of the poorest communities in Allegheny County.

The Rev. Regis Ryan, who heads the nonprofit, said it appears the drain cleaner was spilled accidentally and absorbed by the diaper, though he couldn’t say how that happened, before the staff put it on the girl — apparently without noticing the substance.

“I can certainly say it was a really unfortunate and terrible accident. From everything I heard, there was no intent at all,” Ryan told the AP.

Lazzaro said the girl’s mother has a sealed bag containing at least one more diaper and the baby’s shirt — which appears to be stained with drain cleaner — but said he hasn’t had time to have the items tested by a lab.

The state Department of Public Welfare is investigating, but spokesman Michael Race said only that the department received a report of an injury he can’t disclose.

Mike Manko, a spokesman for Allegheny County District Attorney Stephen Zappala Jr. said the incident has not been referred to that office for prosecution.

Ryan said precautions are being taken to prevent similar incidents, but he did not specify those measures.