A horse collapsed and died shortly after taking the lead during a race in Maryland over the weekend, marking at least the 12th racehorse to die this year in the state. Follow the Petals, a 5-year-old mare, apparently suffered a heart attack, according to the Baltimore Sun.

A necropsy was expected to be performed. Sunday's death brings the number of horses to die during a race in Maryland to at least 10, the newspaper reported, citing the Maryland Racing Commission.

Two other horses have died during training. A video posted to YouTube by the Maryland Jockey Club shows Follow the Petals taking the lead in Sunday's mile-long race at Laurel Park as the six horses go down the stretch.

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The video then cuts to the finish line with the announcer noting that Follow the Petals had collapsed. Jockey Frankie Pennington wasn't injured in the incident, a track spokesman told the Sun.

Follow the Petals won two of the seven races it started this year and came in second place in two more races, according to Equibase. The horse had started 35 races during its career with winnings totaling just over $200,000.

Sunday's death comes after 29 horses have died at California's Santa Anita Park since December. The Stronach Group owns Laurel Park and Santa Anita.

The group has called for medication rules in horse racing to be reformed. Last week, Santa Anita announced the formation of a five-member review team to evaluate horses before the final races of the season and decide whether they're healthy enough to race.

Santa Anita's season ends Sunday. In a statement to the Sun, the advocacy group People for the Ethical Treatment of Animals called on Maryland to follow the Southern California track's example.

"Dead horses will no longer be ignored by the public," PETA Vice President Kathy Guillermo said.