The Utah Medical Examiner found the deaths of Rebecca Toone, 4, and Rachel, 15 months, were caused by inhaling phosphorus, The Salt Lake Tribune reported. The girls became sick in February shortly after an exterminator used a phosphine fumigant on burrows made by voles -- small rodents -- in the lawn around the Toone family home in Layton.
New regulations announced Wednesday by the Environmental Protection Administration ban the use of aluminum and magnesium phosphide fumigants at residential areas and schools, except for athletic fields. The previous regulation banned them from use within 15 feet of a home.
The chemicals will no longer be available to the public, with sales limited to licensed exterminators.
Prosecutors in Utah are still trying to decide whether to bring charges against an exterminating company or an employee of the company who came to the Toone home.