Authorities in Puerto Rico are investigating the deaths of 35 cats at a horse racing facility, police said Tuesday.

A security guard making the rounds at the Camarero Hippodrome in the northern town of Canovanas found the dead cats and called police, authorities said in a statement. A message left at the track complex was not immediately returned.

A necropsy was underway on one of the cats to determine what killed the animals, police said, adding that poison was suspected.

ON THIS DAY IN HISTORY, AUGUST 18, 1934, BASEBALL STAR ROBERTO CLEMENTE IS BORN 

North America Fox News graphic

Police in Puerto Rico are investigating the deaths of 35 cats at a horse racing facility. (Fox News)

CLICK HERE TO GET THE FOX NEWS APP

Puerto Rico approved a law in 2008 to prosecute animal cruelty. The law was signed in the U.S. territory a year after animal control workers seized dozens of dogs and cats from a public housing project in northern Puerto Rico and threw them over a bridge.

Witnesses said at the time that many of the discarded animals were dead but some were still alive when they were tossed.