Stockton, CA – A man and woman were found dead on a houseboat Friday morning around 4 a.m., according to the San Joaquin County Sheriff’s spokesperson Andrea Lopez.

Lopez said the Sheriff’s department received a call from a woman who was traveling with pair, saying she found them dead.

When the Coast Gaurd and firefighters arrived on the scene, their carbon monoxide detectors were going off.

Officials believe the two died from what appears to be accidental carbon monoxide poisoning.

The sheriff’s department is not releasing the deceased identities or their relationship.