A loaded ghost gun was recovered at the scene of a deadly Seattle shooting over the weekend, police said Tuesday as they continue to search for a possible third suspect.

The weapon was found on a 15-year-old who is suspected of being one of the shooters at the Bite of Seattle food festival Sunday, where three people were killed and four were injured. The teen was taken into custody and remains in juvenile detention, according to police.

“Ghost guns” are firearms that can be assembled at home from parts purchased online. Those parts are often obtained without background checks and do not have serial numbers, which would make the gun traceable.

Police found a polymer .89 millimeter firearm with an extended magazine. It had a 33-round capacity and 19 rounds remained in the magazine when investigators retrieved it, Chief Shon Barnes said at a news conference Tuesday afternoon.

A second gun, which police do not believe was used in the shooting, was found with a full seven rounds in its standard magazine.

Police retrieved a third gun, a Glock model 45 .9 mm pistol with a fully automatic switch. Twenty-one out of 40 rounds remained in the magazine, Barnes said.

In total, 14 shell casings from two weapons were found at the scene. The guns had not been reported stolen, police said.

“We have dozens of pieces of digital evidence to review and are continuing to review that information as well as searching the area for more,” the chief told reporters.

Since Sunday night, the Seattle Police Department has received more than 80 calls to its tip line, Barnes said.

Investigators have said there may have been a third person in the gunbattle that they say also included the 15-year-old and his 19-year-old “associate,” Junior Cee Niko Semo, who died of multiple gunshot wounds.

The shooting began shortly after 6 p.m. Sunday at the popular food festival, near the famous Space Needle landmark. Two bystanders — Ashley Whitehead, 56, and Carlos Israel Sanchez Villalba, 44 — were killed by gunfire.

Four other people sustained non-life-threatening injuries.

Police said there is potentially an additional survivor who self-reported to a local hospital with a gunshot wound and then left after being treated. Because of “legal barriers,” Barnes said, police do not know the person’s identity.

“If you are that person, please reach out to us,” the chief said. “We would like to make sure, No. 1, that you’re OK, and No. 2, if you would like to speak to an investigator, please reach out to us so we can determine if you may have seen what happened.”