BOSTON – A 4-month-old boy from Middleton, Mass., died Monday of arsenic poisoning after a special medicine was rushed from Maine in a last-ditch effort by doctors to try to save him.

Maine and Massachusetts state police raced 240 miles from Bangor, Maine, to Boston’s Children’s Hospital, braving traffic to deliver the drug, according to the Essex District Attorney’s Office, which is investigating the poisoning along with the Department of Social Services.

The baby’s parents were at a private party in Nahant on Saturday when they asked for water for their two children – the baby boy and a 2-year-old daughter.

After drinking the water, the children became increasingly ill and the parents brought them to Beverly Hospital, according to a statement from Essex District Attorney Jonathan Blodgett.

They were transferred to Children’s Hospital, the regional poison control center, after it was discovered that the children had ingested arsenic. Hospital officials sought the drug DMPS, which is not approved by the Food and Drug Administration but may be used to treat arsenic poisoning in extreme cases, Children’s Hospital spokeswoman Michelle Davis said.

The medicine was located at Eastern Maine Medical Center in Bangor, which treated people in April who drank coffee tainted with arsenic at their church in New Sweden, Maine.

Rainy weather made it impossible to airlift the medicine, so a Maine trooper picked it up in Bangor. It was handed off Sunday just before 5 p.m. to a Massachusetts trooper at the Maine-New Hampshire border.

Davis would not say whether the drug was administered to the baby before he died. She also declined to release the condition of the 2-year-old girl.

The Department of Public Health tested samples of the baby’s formula early Sunday, which was found to have “very high levels” of arsenic, said spokeswoman Roseanne Pawelec.

An autopsy will be conducted on the boy tomorrow by the state medical examiner’s office, according to Blodgett’s statement.

Arsenic is used in rat poisoning, pesticides and wood preservation. The effects of poisoning vary, including sore throats, nausea, vomiting and death.

Children’s Hospital typically uses the common antidote for arsenic poisoning, British antilewisite, said Davis, adding that DMPS is used only in extreme circumstances.