The British woman killed after being exposed to a deadly nerve agent must have handled the poison’s container, officials said Monday.

Dawn Sturgess and her partner, Charlie Rowley, were exposed to a “high dose” of the toxin when they picked up something containing the Novichok agent on June 30, said Neil Basu, the Metropolitan police assistant commissioner, according to the Independent UK.

“Their reaction was so severe it resulted in Dawn’s death and Charlie being critically ill. This means they must have got a high dose, and our hypothesis is that they must have handled a container,” Basu said.

The “focus” of counter-terrorism investigators is finding the vessel they handled, he said.

According to CBS News, the container is likely a syringe or vial.

They are also looking into where the couple came in contact with the poison, including searching the Queen Elizabeth gardens, a Salisbury homeless hostel where Sturgess, 44, lived and a red Ford Transit van 45-year-old Rowley traveled in hours before being rushed to the hospital.

“It is both shocking and utterly appalling that a British citizen has died having been exposed to a Novichok nerve agent but make no mistake we are determined to find out how Dawn and her partner Charlie came into contact with such a deadly substance,” Basu said.

Officials are still “unable to say” whether the nerve agent in this incident is linked to the attack on former Russian spy Sergei Skripal and his daughter in the same town of Salisbury.

Sergei and Yulia nearly died of exposure to Novichok left on the front doorstep of his home in March.

The British government has accused Russia of poisoning the Skripals but Moscow has denied any involvement in either incident.