SALT LAKE CITY (ABC4) — Six dogs have died following a visit to a training area in Salt Lake City, according to the Utah Division of Wildlife Resources. Testing is underway to determine whether their deaths are linked to a gray substance found near a pond in the area.

The Lee Kay Wildlife Conservation Training Area is now closed until further notice after DWR officials received a report on Saturday, May 20, stating that six out of 13 dogs have died after spending several days in the area.

On Friday, May 12, a dog owner reportedly brought 13 of his dogs to the area and let some of them roam around the pond in the training area.

A few days later on May 17, one of the 13 dogs reportedly began to vomit and showed signs of diarrhea. The dog ultimately had to be put down at the vet. Over the next several days, DWR officials say five more dogs had to either be euthanized or had died of cardiac arrest.

DWR officials are teaming up with the Utah Division of Water Quality to determine the cause of death of the six dogs. DWQ staff visited the site on Monday, May 22, and found no visual signs of harmful algae growth in the pond.

However, they are reportedly looking into the possibility that the dogs may have come into contact with a type of bacteria, which may come from a gray crusty substance found on the shoreline. The gray substance may have emitted a musty odor that had attracted the dogs, according to DWR.

“We are working with the Utah Division of Water Quality and will work to take the needed precautions to ensure safety of visitors at the training grounds before reopening the area to public use.” said representatives of DWR. “Public safety and the wellbeing of the dogs that use this facility are a top priority for us. Our heart goes out to the dog owner for the unfortunate loss of these dogs.”

Tests on the substance are underway to find out whether it has anything to do with the dogs’ death.