Some 29 horses have died at the California course

Trainers are being investigated to see if they played any role in the string of horse deaths at Santa Anita racetrack this year.

Some 29 horses have died at the California course, and many wonder if the unusually heavy rainfall caused problems on the dirt track this season, though the death toll is lower than in recent years.

The California Horse Racing Board (CHRB) is investigating that and has experts examining the remains of the dead horses for clues.

They are also working with the Los Angeles County District Attorney's Office, which launched an inquiry into "whether unlawful conduct or conditions affected the welfare and safety of horses."

The CHRB, which governs the sport in the Golden State, declined an interview request from CNN. Results of the inquiry are expected sometime after the Santa Anita racing season ends Sunday.

Horses exercise at Santa Anita, which hosts its final meeting of the season this weekend.

Jim Cassidy, president of California Thoroughbred Trainers, an industry association, pointed to how the track owners responded to extremely wet weather at Santa Anita, which is usually arid, especially in the summer.

"They kept sealing the track. But, unfortunately, every time you seal it, the pad underneath gets harder and harder," he said.

But there are other issues, said Stefan Friedman, spokesman for The Stronach Group, which owns Santa Anita.

"It's not just the surface they're running on. There are medication issues," he said.

That's a question now being raised: Were trainers running unfit horses and using excessive medications?

Some 25 trainers have lost horses at Santa Anita this season, including Cassidy. Asked what happened, he said: "We haven't figured that out yet."

Many wonder if the unusually heavy rainfall caused problems on the dirt track this season.

Hall of Fame trainer Jerry Hollendorfer has lost three horses at Santa Anita since December and another two at Golden Gate Fields near San Francisco, another track owned by The Stronach Group.

He has amassed nearly $200 million in earnings over a storied 40-year career. He's also been sanctioned 19 times by the CHRB since 2006, for overmedication or use of illicit medications on horses. CNN found no evidence of any successful appeals.

Hollendorfer is among the trainers whose records and actions are now under scrutiny by the Santa Anita owners. He declined to speak CNN.

"We've just gotten some information about what he's done and his violations," Dr. Dionne Benson, chief veterinary officer for The Stronach Group, told CNN. "And so, we're considering whether he will be, every trainer, we're considering whether they will be welcome back to Santa Anita."