UNION CITY — In the latest bizarre death investigation to hit Union City, police are struggling to identify the badly decomposed body of a man after a grisly discovery in a car.

It’s not just that the body of “John Doe” had been sitting in a parked vehicle for weeks that has made the investigation challenging. He was possessing or surrounded by documents, money cards and identifications for at least nine different people, authorities say, raising the possibility that the man’s true identity was one of these — or none of them.

The state of decomposition has added to investigators’ struggles. More than two weeks after the man’s body was found, he remains unidentified.

Police were called to a section of Third Street for a report of a suspicious car, and ended up finding the man’s body inside, authorities said. His cause of death has not been determined either but he appeared to be lying down inside.

Documents and IDs, including passports, cash cards, credit cards, gift cards, tax forms and even a bar association document were found throughout the car. It hasn’t been ruled out that one of these could contain the man’s true name, authorities said.

The past year saw several bizarre and horrifying death investigations in Union City. Last summer, police were searching for a missing 95-year-old woman when they found the body of a man on her toilet. The woman was later found safe, authorities said.

A week before Halloween, family members of a missing Hayward man began receiving texts from his phone, but then his body was discovered in a Union City dumpster. Police say the texts were really sent by the man’s son, who has been charged with murder. Finally, in November, police found a dead fetus in an abandoned home and opened a criminal investigation.