Inquiries into the fatalities, which occurred either in training or as a consequence of racing, have focused on the course's surface which has been called "deep and uneven".
Ed Gregson, a trainer, even likened Del Mar to a "ploughed field " and warned that horses should not be exercised for more than 10 minutes at a time following renovation breaks.
The track's large horse population, numbering 1,800, has also been singled out as a cause.
Joe Harper, Del Mar's president, said: "I'm not saying that the track isn't partially to be blamed. We got started a little late on the renovation works because we were waiting to see if the sports grids added to the Hollywood Park surface would work. By the time we decided not to go that way, we didn't have as much time to get the track the way we wanted it.
"Our breakdown rate is now at about the same level for the whole meeting. However, even if another horse doesn't break down during the meeting, we've still broken down too many.''