A two-year-old girl and her four-year-old sister died Wednesday and five other family members were hospitalized after being poisoned by pesticides in their Jerusalem home.

The girls, later named as Avigail and Yael Gross, were rushed to Shaare Zedek Medical Center along with the rest of their family but doctors were unable to save their lives.

Two of their brothers, Yitzhak, 5, and Michael, 7, were in critical condition, while the parents, in their thirties, and one other brother were in light to moderate condition Wednesday night. The two boys in critical condition were transferred to Schneider Children’s Medical Center of Israel, located in Petah Tikva, to receive specialist treatment. Both boys suffered severe damage to their cardiac muscles and doctors were fighting to save them, but the hospital noted that there was no known antidote to the toxin and that their lives were “definitely in danger.”

The family’s apartment had been treated with aluminum phosphide a day earlier. When combined with water, aluminum phosphide reacts to release phosphine, an extremely harmful gas.

Avigail and Yael Gross (photo credit: Courtesy family)

Avigail and Yael Gross (photo credit: Courtesy family)

Dr. Ofir Marin, head of the trauma ward at Shaare Zedek, said the two boys’ conditions were rapidly deteriorating.

“It’s a tough poison that harms all of the systems, and we are fighting for their lives,” Marin was quoted by Ynet as saying. “We received information from the poison center in Haifa that there’s no drug that can combat this toxin, which harms every organ in the body.”

Aluminium phosphide, also known by its trade name phostoxin, was applied in the apartment by a certified exterminator, but police investigating the scene found “very, very high concentrations” of the poison. The Environmental Protection Ministry, which oversees pest control, stated that though the pesticide was approved for use in Israel, the dosage used at the house was apparently well over the dosage suitable for home use.

According to Channel 2, between 2008 and 2012, 63 Israelis were hospitalized for phosphine toxicity.

Police arrested the exterminator on suspicion of criminal negligence and questioned him. An initial investigation found a pesticide container that was left behind in the apartment.

Paramedics who arrived at the scene described how they found the children scattered throughout the apartment in various states of consciousness and tried to administer first aid before taking them to hospital.

Two of the paramedics who treated the family were hospitalized later on Wednesday at Shaare Zedek as well after they both said they felt sick, Walla reported. The report did not specify the paramedics’ condition.

According to Israel Radio, the apartment, on Shahal Street in the Givat Mordechai neighborhood of the capital, was fumigated on Tuesday. The exterminator who carried out the work left after giving safety instructions to the parents.

The report said that some of the children had already begun to feel ill later that evening.

The parents took their children to a clinic and told medical personnel that the family were unwell, but it was believed they were suffering from indigestion after eating rotten eggs and cheese.

“Nobody suspected that it was poisoning,” a family friend who spoke with the father told Ynet.

The family was released home by the clinic after undergoing a series of tests. Following the deaths of the children, the clinic issued a statement expressing regret over the loss of life, but claimed no symptoms of poisoning were discovered in the tests.

“The tests did not uncover any suspicious finds,” the statement read. “After receiving the results of the tests and providing treatment for nausea, [the clinic] released the family home.” The clinic said it had launched an investigation of the incident.