Laurel Park in Maryland on Tuesday began allowing horses to ship into the track, but no horses, including the ship-ins, will be allowed to leave the grounds until Maryland agriculture officials lift a hold order on a barn where a filly tested positive for equine herpesvirus, according to track and agriculture officials.\nThe hold order will likely be in place until Dec. 6, 21 days after the filly first began exhibiting signs of the highly contagious disease. The filly, a 2-year-old named Nin trained by King Leatherbury, was euthanized on Saturday.\nLaurel Park shut its grounds last Thursday because of concerns about containing any potential outbreak of the disease. As a result, the track&#146;s cards on Friday and Saturday suffered from dozens of scratches of horses that were planning to ship in to race.\nSince the filly tested positive, no other horses on Laurel&#146;s grounds have exhibited signs of the disease. All 31 lead ponies at Laurel have tested negative, and the 25 other horses in the barn have tested negative as well, according to state agriculture officials.\nEntries for this week&#146;s races are relatively strong. The nine-race Wednesday card drew 84 entries, and the Thursday nine-race card drew 94 entries.\nJulie Oberg, a spokeswoman for the state agriculture department, said that the hold order on the barn where the filly tested positive could be lifted sooner than Dec. 6 if no horses show any symptoms of equine herpesvirus. \nWhen the hold order is lifted, Laurel will begin to allow horses to leave the grounds, according to Mike Gathagan, a spokesman for the track. \nLaurel Park was placed under a hold order in 2006, when an outbreak of the disease in Maryland killed four horses at Laurel and Pimlico. Officials of the track and the state agriculture department have been extremely cautious about containing any outbreaks of equine herpesvirus since the deaths.