BRONX - Officials have released new details surrounding the deadly Metro-North train derailment in December. 

Newly released documents show the train's engineer, William Rockefeller, had severe sleep apnea. 

The NTSB did not say whether Rockefeller's disorder contributed to the derailment in the Bronx that killed four people and injured 70 others. 

Drug tests on Rockefeller after the accident revealed only small amounts of aspirin and an over the county antihistamine.