(CNN) -- A BP executive and a company manager aboard the doomed oil rig Deepwater Horizon were designated "parties in interest" Thursday by the investigative board probing the worst oil spill in U.S. history.
The designation given to Pat O'Bryan, the company's vice president for well drilling and completions, and site manager Robert Kaluza indicates their actions are under scrutiny by the joint Coast Guard-Interior Department investigation into the disaster. It also gives them the right to examine documents collected by the board and to have attorneys in the board's hearings cross-examine witnesses on their behalf.
The news was announced by Capt. Hung Nguyen, the Coast Guard's top representative on the board, at the end of another day of hearings into the disaster. The board has one more scheduled day of testimony in the New Orleans suburb of Kenner, Louisiana.
O'Bryan was visiting the platform the day of the April 20 explosion aboard Deepwater Horizon, which sank two days later and uncapped an undersea gusher in the Gulf of Mexico. He is listed as a witness in the next round of hearings by the investigative board, set for late August in Houston, Texas.
Kaluza, one of the BP "company men" aboard the doomed rig, has twice invoked his Fifth Amendment right against self-incrimination in previous hearings. The other "company man," Donald Vidrine, has been excused from testifying for medical reasons.
BP leased the rig from Transocean, whose crew operated the offshore platform. Several top officers aboard the rig, including its captain, chief engineer and offshore installation manager, also have been named as parties in interest to the investigation.
The designation sparked criticism Monday by lawyers for rig Capt. Curt Kutcha and Jimmy Wayne Harrell, the offshore installation manager. Their attorneys argued that the board should have given them that status before they testified during an earlier round of hearings in May.