New York ? With weather and mechanical problems all but ruled out as causes, investigators said Friday they had demanded blood and urine samples from the pilot in the Staten Island ferry wreck to determine if his medication played a role in the full-throttle crash.

At a briefing near the crippled vessel, National Transportation Safety Board Chairwoman Ellen Engleman provided new details about the investigation that suggested authorities were focusing on the human element in Wednesday’s wreck, which killed 10 passengers.

She said a federal subpoena was issued for tests that could determine if blood-pressure medication taken by Assistant Capt. Richard Smith may have contributed to the wreck. Smith attempted suicide shortly after the crash and remains hospitalized.

Investigators also said they would interview the ferry’s captain, Michael Gansas, whose whereabouts at the time of the crash have been the subject of speculation. Authorities were looking into whether Gansas was in position to take over for the pilot if he were stricken.

Gansas told investigators that he saw Smith slumped forward over the throttle just before the crash.

No criminal charges have been filed against Smith, although authorities said he immediately fled the scene of the accident, leaving behind dozens of maimed and injured passengers. Three people lost limbs and more than 60 others were injured as the ferry slammed into a concrete pier.

Tests have indicated Smith was not drinking or using illegal drugs before the accident.

Federal investigators have not spoken to Smith because of his medical condition, Engleman said, and it was unclear when they might be able to interview him. Smith’s attorney has said his client’s family hoped “people will not rush to judgment.”

Gansas is scheduled to meet with the NTSB on Tuesday. Authorities are expected to ask whether he was in the wheelhouse with Smith at the time of the crash.

City procedures — but not Coast Guard regulations — require both men to be there when the ferry is moving, but investigators say they have received conflicting reports as to the captain’s whereabouts. Gansas has retained an attorney, but union and city officials have not identified the lawyer.

Gansas did not return messages left at residential numbers listed in his name in New Jersey and Staten Island.